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205: Infiniti Q50 Dual Throttle Lean Condition
205: Infiniti Q50 Dual Throttle Lean Condition
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About this episode
A deep dive into diagnosing a 2015 Infiniti Q50 with persistent lean codes on both banks. The host walks through extensive testing including fuel pressure, vacuum leaks, sensor data, and the unique dual throttle and dual mass airflow sensor setup. Despite initial confusion over a non-functional MAP sensor and dirty air filters, the breakthrough came from replacing both mass airflow sensors, which restored proper fuel trims and improved performance. The episode highlights the challenges of diagnosing complex systems, the importance of known good data, and practical tips like loading the engine to detect vacuum leaks and conducting VE tests.
Topics:
infiniti q50
lean codes
mass airflow sensors
dual throttle system
vacuum leak diagnosis
fuel trim analysis
map sensor confusion
ve testing
diagnostic strategies
sensor calibration
On this episode I go through the diagnosis of a 2015 Infiniti Q50, 3.7L V6, with a P0171 and P0174, lean condition. I'll share my thought process through the diagnostic steps tracking down the source of the positive fuel trims. My goal on this show is to share vehicle diagnostics that challenge me to come to a precise conclusion, this vehicle being one. I have a gut feeling I know the solution, but not enough data to condemn a part.
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"...f the episode I was talking about a 2015 Infinity Q50, that I was having some lean codes and kind of ra..."
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Hey, what's going on?
Automotive World.
Welcome to another episode of the Automotive Diagnostic Podcast.
My name is Sean Tipping and I'll be your host once again for this episode.
Thank you for joining me this week on the show.
I'm going to do a bit of a conclusion to one.
If you listened to the episode with Ben Varnadoe, at the beginning of the episode I was talking about a 2015 Infinity Q50, that I was having some lean codes and kind of ran out of tests in my initial visit to the shop.
I did end up getting this one fixed, so I wanted to go through that with everybody.
So if you listened to that episode, you know a little bit about this car.
I'm going to go over some of those details again.
So a little bit of a review, but I will give some more detail on the specifics so that you have all the information.
The case studies that I've been sharing recently and that I want to continue to share more of are vehicles that I struggle on because there's plenty of those, but I think it's really important to get that information out there.
You know not only what the fix for the vehicle is and helpful tips that might help you get through some of these things, but just sharing that.
Hey, everybody struggles when we're trying to do this stuff at any level within the field, especially a high level, even if we're trying to work on all makes and models.
It is challenging a lot of the time and it's not always a quick and easy solution, but there are ways to work through it, there are ways to get to the conclusion, but that's kind of what I want to share, with as many case studies as possible, this being one of those, because it was not a quick and easy one, for me at least.
But let's go through this Again.
2015 Infiniti Q50,.
This is the 3.7
liter naturally aspirated V6 motor.
This is not the hybrid version.
The shop called me in because they were having lean codes.
They identified a P0171, p0174 lean on both banks.
They kind of ran through their initial testing and weren't able to come to a definitive answer as far as why it was running lean.
According to the customer, this thing was running fine and then all of a sudden it started running poorly and the check engine light was on and the shop noticed the same thing is occasionally this thing would kind of miss and sputter, mainly at idle.
They were noticing this and the check engine lights on.
With the lean codes they identified positive field trims and again they went through some of their basic checks.
So I was told by the tech that checks that they did is they smoked the intake to check for vacuum leaks.
They checked the fuel pressure and he actually still had a gauge hooked up to this.
They teed a gauge in back by the fuel tank and they had the pressure gauge there with the back seat up.
When I got to the vehicle he did verify that the fuel pressure was adequate according to the specification that he found, which is around 50 pounds of fuel pressure and that was all time.
So whether it be idling or going down the road, it maintained adequate fuel pressure.
Other than that said, he went over kind of the basic sensors in the scan tool, looked at mass airflow, cooling temperature, intake temperature, airfield ratio sensors, that sort of thing, just to see if there's anything out of place, and he wasn't able to identify one thing that be causing the entire engine to run lean.
It's both banks and both sides are relatively equal in the amount of positive trims that they have.
And this is the information he's telling me.
Of course I want to verify all that.
So I get the keys, check out, the car, verified everything that he was telling me and it was all right on the money.
Fuel pressure was adequate both at an idle and under a load.
I actually did get a fuel sample because the gauge that was teed in has a little relief valve and I've said it on the pod before If you're checking pressure, just get a sample.
I've made that part of my routine for any vehicle.
I'm taking a fuel sample if I'm checking the pre, if I'm going that far right and this guy kind of already did it for me, which was nice.
But if I've got a gauge on there, I'm getting a fuel sample, especially if I'm chasing a lean condition.
But there's been a ton of cases where I've had really strange things go on with the fuel, whether it be water, ethanol, e85 or some sort of just weird contamination.
I had one that looked like mud.
I don't even know what was in there, but it sure wasn't fuel.
I had a Kia with E30 that made it run really, really weird.
I should say not weird, but when it was lean and when it was not lean was very odd on this Kia and it was E30 that was in there, not E85 and not the E10 to 15.
That's normal pump gas, but E30 was enough to throw this non-flex fuel Kia off.
So, anyways, I get a fuel sample from this thing and it's just normal pump gas and as far as I can tell, this Infiniti is not a flex fuel vehicle.
Anyways, there's no percentage for ethanol content that I could find in the scan tool, or usually I'll check back by the gas tank and I'll I'll go to the filler neck and I'll see if it even indicates that it's a flex fuel vehicle or not, and this one didn't appear to be one.
So, and the gas was normal pump gas with about 10% ethanol.
That is eliminated and that's definitely something that can cause your engine to run lean if it's not set up for flex fuel.
But you do put E85 in there, but not the case.
So I go through scan data and I do find the codes, the P0171174 lean.
For both banks the trims are elevated in the positive direction, meaning the computer is adding fuel to compensate for a lean condition.
It did get into fuel control when the long terms were up between 20 to 30 percent.
Then you could see the short terms bounce, you know, back and forth to zero at that point and actually ran pretty well once the trims had compensated and it got into fuel control.
Now what I did find is if I went into the work function area of the scan tool and I reset the trims, just something I like to do is just sometimes that can fix a car right, like sometimes the fix could be made to a vehicle and, depending on the application in the computer, you need to reset the fuel trims in order to get the engine to run correctly.
Otherwise it may take a while for those two trims to reset on their own, and you might think the car's still broken, when really it isn't.
So I like to do that.
And then I also like to see what happens after I reset the trims.
Right, maybe it's fixed, but do they bounce right back to where they were and does it run poorly in that period of time?
Right, like after I reset the trims, it does this thing actually start to run lean, which this one did.
You could tell it was like sputtering and misfiring as soon as I reset those trims, and then the short terms skyrocket up in the positive direction and then eventually the long terms will catch up and then it starts to run okay again.
Once it gets into fuel control, it compensates for that lean condition.
It's running pretty well, okay.
So as far as I can tell, this thing is actually running lean.
Now my next question is is when is it running lean?
Now I'm sitting here in the parking lot, so I know it's at idle, but is it running lean under a load?
Right, not just necessarily elevated rpm, but under a load, and this is one thing that can help you pick out a vacuum leak pretty quickly and you want to either power, brake or drive the vehicle in this case, because the load key is the really important part here on a mass airflow sensor vehicle, which this is and I should actually mention this is a mass airflow sensor vehicle, but it has two mass airflow sensors and two throttle bodies, which does make this one a little bit unique
, something that I'm not used to.
I haven't diagnosed a ton of drivability issues on a dual throttle, dual mass airflow system engine, but that's what this one is and I'll talk about that more as we go because it kind of threw me off a little bit as far as figuring out what was wrong.
But on a mass airflow sensor engine, if you want to quickly identify if you have a vacuum leak, if that's what's causing your lean condition, load the engine up, just power brake it or go drive it and watch your trims at that time under the loaded state versus the idle state, and what you're doing is you're bringing the pressure inside of the intake manifold closer to atmospheric, right, you're putting the engine under a load, meaning
you're opening the throttle and you're equalizing or bringing it closer to equal pressure the outside and the inside of the manifold, which then basically gets rid of the vacuum leak.
Right, a vacuum leak is only there because there's a difference in pressure between the outside atmospheric pressure, you know roughly, let's say, 15 psi on the outside of the manifold, and then all of the pistons pulling against the back of the throttle blade on the inside of the manifold creates that vacuum, the lower pressure than atmospheric.
And so atmospheric pressure is going to find its way in through any leaks, right, a blown out gasket, a torn hose, whatever the vacuum leak is right.
But if I load that engine, I am now bringing that pressure in the inside of the manifold.
By opening the throttle and allowing the engine to run at a higher rpm under a higher load, I'm equalizing those pressures, and so any any opening, whatever vacuum leak is, isn't necessarily a vacuum leak, right?
All the air is going to be going in through the throttle.
There's not a difference in pressure, so that leak really isn't a leak anymore.
So what I'm getting at there is is your trims will now retreat back towards zero.
If that's the case, okay, um, and I do want to make a note here and I learned this from one of John Thornton's classes a long time ago, so I'll give him credit here but don't just rev up the engine in parker neutral.
If you look at the manifold vacuum, when you do that, you actually increase the manifold vacuum.
Let's say I just bring the engine up to like two grand in parker neutral, the manifold vacuum will go up as or you could say, the pressure would go down.
If you're watching a vacuum gauge, you'll go from like 17 inches of vacuum to 20 inches of vacuum when you rev up the engine in park, because what it is is a freewheeling engine doesn't require much load to spin faster, and so you get just a little bit of a throttle opening.
But now you have that many more intake strokes happening against the back of that throttle and you actually increase the vacuum.
So what I'm, what I'm getting at there and what John taught me years ago, was that you are actually amplifying the vacuum leak.
In that case you're creating more of a pressure difference between the outside, the inside of the manifold, and so just revving up an engine in parker neutral and mass airflow sensor engine really isn't going to point out a vacuum leak to you.
You need to load it.
That's the key.
So power break it or go drive it.
Anyways, I did that.
It's lean all the time.
Okay, so I can say with somewhat confidence that there's not a vacuum leak.
There are some other checks we can make.
The tech did say they smoked the intake.
I try to take information like that with a grain of salt because I want to do it.
I want to see it myself because I don't know how is the test done.
You know what was overlooked.
There's endless variables.
I always like to see the test for myself.
I don't take that stuff, you know, in stone.
So we're lean all the time.
I'm going to go through with my scan tool and I check all the you know, important sensor data pins that could be affecting this.
Of course we're going to look at stuff like engine coolant temperature, air intake temperature, look at the air fuel ratio, slash oxygen sensors.
So it's air fuel ratio sensors on the upstreams on this and their oxygen sensors on the downstream.
Make sure that those are all in agreement.
And for an engine that is Lean on both sides, you know a V-style engine with two banks and and I should say they're both equally lean, right, so the trims are positive in an equal amount between the bank one and bank two.
The odds of it being air-fuel ratio or oxygen sensor caused, although possible, is probably unlikely because they have to be both failed and both failed in the same way, which, again, okay, it could happen, but it's unlikely.
But I'll take a look at them and they're all in agreement.
And when I say that, both side-to-side, but front to rear as well, right, if you have an air-fuel ratio sensor that is not reporting properly, it's gonna say, hey, it's rich when it isn't rich, or it's lean when it isn't lean.
Your downstream sensor is gonna tell the truth there, right?
So let's say, let's just, this is not this car.
But let's say, air-fuel ratio sensor upstream is saying, hey, the engine's really lean, that's, it's what it's reporting.
So the engine responds by increasing the fuel trims, adding more pulse width, injection to the fuel injector, adding fuel to the engine.
Right now, if that air-fuel sensor is not actually reading correctly, and now you're adding fuel to an engine that wasn't running lean, you're gonna get a rich condition, right.
Who's gonna see that?
The downstream sensor is gonna see that and report that, right, so you can look at the front and rear and see are they both reporting correctly or you know, it was one line.
Essentially is what I'm looking at there, they all look alright and, again, unlikely that that's the cause of my problem, but I do want to check that out because air-fuel ratio sensors are a big input here as far as driving fuel trims, so those look okay.
Now I've got two other sensors here that are also important to fuel delivery, and these two sensors are kind of where I got through off a little bit and was difficult to make a call.
I'll start with mass airflow sensor.
Now again, this is two mass airflow sensors and they each have their own individual data pins and then there is a total grams per second airflow into the engine.
Now, I wasn't 100% because it doesn't spell it out.
I was like does it add the two together and just make a total?
I think that is what it does, or is it doing some sort of weighted calculation?
Is there something else happening?
I wasn't a hundred percent sure, but you could see the individual sensor pins and you could see the total air volume going into the engine.
I should point out the sensor data pins were in voltage and the total was in grams per second.
Right, so you'd have mass airflow or airflow mass into the engine grams per second, which we used to seeing, and then it had individual mass airflow sensor data pins.
Okay, what I could tell you on my initial inspection this thing was about five to five and a half grams per second of air on a hot engine running in gear at idle.
All right, and I like to make those checks and if you've done any mass airflow sensor stuff, where you're looking to see, is the sensor skewed, you would look to see are the grams per second roughly equal to the engine size in liters.
Okay, so if it's a four liter engine, you would roughly expect four grams of air per second and a hot idle in gear.
Now I can also say that this is definitely not true all the time, I'd actually say a lot of the time.
On newer engines I found this rule of thumb that I could rely on on certain engines to be not true.
So I'll still think about it, but I don't take it, as you know, a 100% certainty that there's an issue.
Okay, now this is.
This is a case two where I'm not gonna weight this too heavily, because five and a half is definitely more than the 3.7
that the engine is.
But even if that was wrong, it's wrong in the wrong direction for the problem that I'm having.
Okay, think about it.
Let's say the 3.7
liter engine and we're reading 5.5
grams per second of air.
If that was incorrect, it would mean that the engine thought there was more air entering the engine than there actually was.
Let's say 3.7
grams per second is normal.
It's not on this engine, but let's say it is.
It would actually be in a rich condition, okay.
So at this point I'm assuming that, even though this doesn't match up with my old school rule of thumb, that it's not my issue because it's higher than the engine size.
Now, could this number still actually be too low?
Yeah, it definitely could, but my problem is I don't have a known good.
I don't know what normal is on this engine, but that's my reading I have at idle for the mass airflow sensors, right, and again, it's a dual throttle, so that kind of changes things too, right.
Of course, there's gonna be an ability for more air to go into this engine than a single throttle engine, so I don't know how that's gonna play out yet, but that's the data that I observed here at idle.
Alright, so the other data pit that I looked at, and just these are some of the basic ones that I'm gonna peek at when I have a fuel trim issue.
The other data pit that I looked at was the map MAP sensor, and this definitely threw me off a little bit, so I want to share this with everybody.
This is was reading on the scan tool data pits to KPA and for reference to KPA, or kilo Pascal's, is 0.3
psi, or it's one half of an inch of mercury, okay, so that's almost nothing and it's definitely not right on a running engine at idle, is it also never changed?
I could rev up the engine, I could do everything, and that value from that map sensor never changed, which I thought was very, very strange.
Now I didn't have a code, right, you should have a P0106 for map sensor performance or something like that, but it's definitely not right as far as what I'm used to seeing.
And I looked and there actually is a map sensor plugged in on the top of the intake manifold, so it's not like it's a data-pid for something that doesn't exist on the vehicle, or so I thought.
So what I did was I unplugged the sensor and I used my sensor simulator.
Right, you get this in the ASC Wave Test Kit.
You can dial in resistance.
You hook it up to the three wires and then you can dial in whatever value you want the computer to see, and what this is proving out is the circuitry to the map sensor and the computer's ability to observe the voltage coming out of the sensor and do something with it right.
And so you can see the value on the scan tool.
You could actually see it in inches of mercury, which was helpful, and I just dialed this into where you would see the intake manifold pressure at idle.
Roughly right, I put it at about 17 inches of mercury at an idle.
That's about what this engine would normally be at.
And so my goal here is to see is does this fix my fuel trim issue?
Okay, well, it didn't do anything.
I reset the trims while I had this on there and it didn't do anything.
And it didn't set any codes pertaining to a map sensor, which again, I thought was very strange, but it didn't change anything.
So I'm very suspicious of this.
But this is a problem Like this is very obvious.
And again, there's a sensor there on the intake manifold, there's a harness, there's a wire.
I can change the value.
So I was talking to the shop.
I was like, well, we should get a sensor for this thing and just let's see what happens, because this is not right.
Well, in the process of doing that, we took out the old sensor and we looked at it.
It's a dummy sensor, meaning that there are no male pins in the sensor itself.
It's got a connector that plugs into it, it's got circuitry, the computer responds to it and the sensor goes into the intake manifold.
It's exposed to manifold pressure but there's no pins on it and this is very confusing.
But we came to the conclusion that it's not used on this application but it must be on others and fast forward to doing my research for this episode.
I didn't know it at the time.
The map sensor is only used on the hybrid applications.
All right.
So you can get a Q50 hybrid, which this one is not.
That one uses the map sensor.
So the map sensor you get for that has pins on it and it actually reads the manifold pressure and the engine computer actually uses the value For this one, the calibration, the software that this engine computer has.
It's basically programmed to ignore it for the non-hybrid version, right.
So all I was doing there was absolutely nothing.
The computer wasn't observing that voltage, even though I could see it on the scan tool.
It's not using that in the fuel calculations.
So that was pretty much a big waste of time.
Okay, so we're still running lean and what I'm kind of down to now is my mass airflow sensors.
But again, I'm not incredibly sure on what's good or what's bad or how I'm gonna prove it on this particular engine.
Now, one thing you can do is a VE test, which I've talked about before, and this involves looking at the engine, rpm, the air temperature, the grams per second into the engine.
You use the engine size, the cylinders and you put all this into a calculator.
I like using the ATG VE calculator.
You can just Google it and it's free.
You put these numbers in, you get a percentage and, generally speaking, on a naturally aspirated engine you wanna see above 90%.
Trouble there is and you'll see that with this engine is, if we're talking about something older like, you really need to consider what you're working on.
If you're talking about something older like, I'm doing a VE test on a 2000 Chevy truck with a 350 in it, with a push rod motor, right, 85% on that might be as good as it'll ever be.
Okay, and that's just that's how that engine breathed right.
It was not as efficient as a newer engine.
I remember when I was teaching in college we would have the students do VE tests on their car and they always loved doing that cause they could put the accelerator all the way down on a test drive and that's always fun for everybody.
But we had like a 21 Toyota naturally aspirated engine that was at like 110% and you might say, well, how could an engine breathe more than 100%?
Well, there's systems on these engines like variable valve lift and cam timing and things like that where you can get over that theoretical air flow through an engine because we're changing the, we're essentially changing the engine dimensions as the vehicle's running and so we get the higher numbers.
So, on that, 85% is terrible.
It's awful right, but again, I like to see close to 90%.
If I see that, I'm usually pretty happy with things.
That's what I got from this when I did a VE test was about 93%.
And the other thing I'm looking at is you know, I looked at the fuel pressure while we're giving it a major load on the engine and it was able to support the fuel pressure that it needed.
I'm trying to feel how is the power on this thing as I'm driving felt adequate power to me Now?
Granted, I drive a 2010 Ford Transit Connect, so just about anything's gonna feel like adequate power to me and I think I need to take that into account when I'm driving some of these vehicles.
But it felt okay to me.
I also like to look at the O2 sensors while I'm in a full throttle mode to see are they going into a rich state?
And they were.
They were pegging rich, meaning that we're supplying enough fuel for this thing, that the O2s are actually going rich, right, that it's not starving for fuel, as far as I can tell.
So the idea of the VE test for me, it can tell you a number of things about the breathing of an engine.
But for me, in this situation, I'm looking at it to help me gauge.
Normally it would be if the mass airflow sensor.
But in this case, are the mass airflow sensors reporting correctly, right?
Are they under reporting?
Is that why we have a lean condition 93%?
I don't know that.
I can necessarily point to them.
Now, one other thing I did notice about these two sensors, both at idle and under a load cause.
I graphed the data on the scan tool.
There was one sensor Bank One, I believe it was, doesn't really matter.
There was one sensor that was reporting slightly less than the opposite sensor.
At all times meaning at idle, mid-load, heavy-load it would report less voltage than the other sensor at a given RPM consistently.
Now I didn't know if this was normal.
It didn't seem normal, but again, this is one of those little things where I'm not super familiar with these engines and I don't wanna go diving down a rabbit hole If I don't know.
Maybe that's just the way this is set up, maybe the way the manifold is constructed, one side gets a little bit more air in than the other, right?
I mean, once the air's into that manifold it's gonna get divided up equally into the cylinders, but does it enter both sides of the engine equally?
I don't know that.
Okay, so the VE test didn't really show me anything, but I still want to take a physical look at these mass airflow sensors, right, and at this point I'm just kinda running through everything that I would normally do.
I don't have anything really point me towards something yet.
I thought I did with a map sensor, but that turned out to be nothing.
But I still have to keep going with testing and just go through everything that I normally would.
So at this point what I'm gonna do is I'm gonna pull out these mass airflow sensors into a visual inspection on them, and not only the sensors but the air filters themselves.
Okay, because, as we all know, the way that the air passes across the sensor can affect its reading.
Okay, so I pull the sensors out, which is easy to do, they're very accessible and they actually look really clean, like not dirty at all, which, obviously, if they're dirty, that's something that can cause a lean condition, but they looked relatively clean.
Now the other thing I looked at was the air filters themselves.
Now, these things were dirty and they were actually kinda collapsed in on both sides Like they'd been in there for quite some time.
I was like, well, maybe this is causing our problem here.
This might be it right.
Here it's just, and there are two different air filters because there's two snorkels going into this intake and they were both aged, both dirty and both slightly deformed.
So I did tell the shop.
I'm like, okay, we need to put some filters in this thing.
That's my next step here, still questioning maybe the mass airflow sensors themselves.
But we gotta get some filters in this thing and reassess.
So they get a couple of filters for it.
We slapped those in there and I reset the trims and it didn't change anything.
The numbers that the mass airflow sensors were reporting were the same.
Oh, and I should mention the grams per second.
They fall load.
I hit about 200 grams per second on this engine when I was doing my VE test and then that idle again.
They were still about five to five and a half.
We're still lean, we're still positive.
Last thing that I wanted to do here because I was kinda running out of tests at this point is I wanted to smoke the intake, and not necessarily just the intake, cause I went through that whole thing of how I was determining hey, I don't think we have a vacuum leak here, but I wanna smoke both the snorkels and the crankcase all at the same time.
Right, because the crankcase has the fresh air breather for the PCV system that goes into the snorkels, that's between the mass airflow sensor and the throttle on both sides.
So it's potential, if we have a crankcase leak, that we could be getting unmetered air into the engine there, right?
So that's a possibility.
And I gave the snorkels a visual and I didn't see any cracks, but that doesn't mean there isn't one.
So what I did was I capped both air intake ducts, the snorkels, right at the mass airflow sensor.
So I would say, just past the mass airflow sensors, I put two caps in there and then I fed smoke into the intake and I just wanna see is there leaks anywhere, not only in the intake but then also in the crankcase and the air ducts?
Do we have any sort of chance for a false air situation to be throwing these numbers at us?
So I did that perfectly sealed.
I actually built up a little bit of pressure.
When I would pull off the dipstick tube or the oil cap you could see smoke coming out of there and there was no leaks anywhere.
And so the shop, they did the smoke test of the intake.
I don't know exactly how they did it, but they were accurate.
There's no leaks there and it confirmed what I was seeing with my scan data, not a vacuum leak.
And now I can say there's not a false air situation here either.
So at this point I'm not entirely confident on what the problem is.
I'm leaning towards mass airflow sensor.
You know your gut tells you something and I'm leaning toward mass airflow sensors.
But I wasn't quite 100% convinced, and partly because they didn't know how the computer took in the values for the mass airflow sensors too right.
I did mention there was one that was less than the other one.
So was one side failed enough to cause the whole engine to be lean?
It's possible, but I don't know that for sure.
Is there anything else on this vehicle that I could potentially be missing?
That's definitely possible too, and so I told the shop.
I'm like, hey, I'm not ready to make a call on this.
Let me do some reading talks to some people and I'll get back to you on this thing.
So with all that, I decided I'll move on with my dakes.
I spent enough time on this and I'll talk to some people.
And that's where having a network comes in.
I know I'm sorry that I say that every single episode, but it is important and I reached out to some friends and got some ideas and you know a lot of it was some of the stuff that I had checked, but some of it wasn't.
You know a couple of people reiterate how important mass airflow sensor inputs are for Nissan's and Finities and that I should really be focused on that.
So PJ Walter sent me a TSB that I did not see in my searching, that had an update for calibration for P0171174.
The updated calibration didn't really pop in my head.
I didn't check for it.
I should have.
I didn't check for it, but the way it was acting didn't seem like a software thing that just decided to change all of a sudden, right.
So I go and I reset the trims.
This thing ran like garbage and, although possible, it just didn't like strike me as a calibration issue.
But you know, I'm like I said, I'm kind of run out of stuff.
I want to verify that that's not the case.
And also I was kind of thinking after the fact well, what if somehow we just have the wrong calibration in this thing, right?
Somebody put a computer in it, somebody programmed at the wrong way?
You know that's a possibility and I never did look at the engine calibration to see if it was correct for this vehicle.
And then I'm thinking of you know what else.
What else can this be?
Obviously the mass airflow sensors are in question.
You know, maybe it's like an injector situation, but I'm thinking that's kind of unlikely since it's pretty equal, the trims being off or equal side to side.
You know, maybe an ECM software calibration issue, that's possible.
But Also those mass airflow sensors, right, and because the filters were again dirty and old and a little deformed, even though they weren't dirty.
I'm really really thinking those mass airflow sensors and again one of the people I talked to is like those are really important on these Nissan's and I think if it had just been a single mass airflow I probably would have told them get a mass airflow sensor for it.
But I was hesitant because of the two.
They just threw me off a little bit.
But I call the shop owner next day.
I'm like, hey, we just order a couple of maps for this thing.
You know, get some high quality ones and I'll come over, will install them and we'll try and we'll see.
I was like this is the most likely thing that is causing your problem, but I'd like to be there and see for myself, if for no other reason, that if it fixes it I can have some known goods right on this particular engine.
So he said, yeah, I'm willing to do that, and so I came back the next day when he had them, I put them in myself.
So I reset the trims and and immediately they were way better than they were before.
So they didn't climb all the way back up, they got up to like about 10% or so.
So I went out and drove this thing got on it.
It had a noticeable jump in power from when I drove it the day before, and so this car actually is pretty, pretty peppy now that it has the correct amount of Airflow being read in the computer.
Now again, I wasn't starving for fuel.
The O2s were pegged and it was.
It accelerated fine, but now it's noticeably more acceleration for this thing with the correct amount of airflow.
After I gave it a few runs the trims actually came down.
I mean, they were like five to eight on the long term and the short terms were bouncing around zero, and so they were right back to where they should be.
So the mass airflow sensors fixed it and both of them and I was again questioning Whether it was one or two of them.
But here's the thing Both of the values were now higher and they were equal.
That was one of my questions.
Was the difference in value a problem?
I think they should be equal on this engine now.
They weren't perfect all the time, but they were real close and when you sat there at a steady idle they were almost identical.
Now, for known goods here, 7 to 8 grams per second is normal at a hot idling gear.
On this thing, wide open throttle were closer to 230 grams per second as opposed to the 200 that I had on my Initial runs on these things.
So it upped the amount of airflow that the computer was using as a base to add fuel, which is exactly why it was lean, right, I mean, makes total sense.
And I think you know a few things.
Had I had a known good as far as airflow goes on this thing, it would have been easy, super easy.
Next time I get one of these things, it'll be super easy.
I'll look at those numbers, I'll compare it to my notes.
Okay, smash airflow sensor.
You know, make your checks and stuff and make sure it's not a an air leak problem or a filter problem.
But once you've verified all that stuff, okay, it's, it's sensor time.
And I also know now that they should be the same value between right and left.
Mass airflow sensor.
Now, the VET test also came back at over 100% on this engine.
Okay, so 93?
Not good for this engine.
It could have be worse.
Oh yeah, definitely right, it could be starving for fuel, but it wasn't quite that case here.
But it needs to be over 100% and I didn't even really consider it until after the fact.
But this engine has Variable valve lift.
It's got a motor on the top of the cylinder head that kind of operates like the BMW valve tronic system where it moves an eccentric shaft to change the depth of the valve opening, and so of course that makes sense.
On how this, things can hit over 100% of the theoretical load for a 3.7
liter Because we can essentially change the engine breathing dynamics as we're going down the road and and again, that was kind of one of the points I want to make here.
With the V test, which is a really powerful tool.
You it's something again where you kind of have to have a known good or at least take it with a grain of salt and really Consider the engine that you're working on.
You know what's good, what's bad.
How's it gonna point me to the direction that I need to be right.
Mass airflow sensors have always been a little tougher to pin point of fault because, as I've mentioned before there a sensor where we can't take a physical measurement To verify the accuracy of the sensor right, I can't Physically measure how much air is going into an engine at a given point.
It'd be fantastic if we could.
That would, I think, me and Brian Mann talked about it.
That would be an awesome tool if I could sell something that you strapped on to the air intake of the engine and it actually measured Air flow accurately and you could compare it to what was you know on the computer from the mass airflow man.
That would make things so much easier.
But as far as I'm aware, such a thing doesn't exist.
But if there is, let me know about it.
I'll buy one right now.
It's not like other sensors, right?
Like coolant temperature sensor, we just measure the temperature of the coolant.
Okay, map sensor, we just measure the manifold pressure.
Right, there's so many.
And you can go on and on like that, like there's so many sensors where you can tell what, if, if what it's measuring is accurate or not, by using another type of physical Measurement.
We can't do that with mass air flows, so it gets a little tricky as far as well.
How much air is actually going into the engine, how much air is supposed to go into the engine?
And that's our, that's our tool there to help us out with maths is known good numbers.
So I guess the final thing that I'd point out here is get as many known goods as you can.
If you're looking at an engine.
You got the scan data up, take a note of what known good for grams per second is at a given point and then put that and Then put that in your notes somewhere so you have that for future reference, because had I had that on this one, it would make it a lot easier.
All right, that's it for today's episode.
I hope you found that interesting and helpful.
Like to appreciate everybody out there for listening all the feedback I get on the show.
I always appreciate that, but without all the way, let's get out there, start fixing the world, one card at a time.
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