The 2008 Mazda RX-8 uses a rotary engine, which is different from the usual piston engines. Because of that design, problems after a rebuild—like losing power or going into a protective mode—can be tied to how the engine’s internal seals and compression are behaving.
A rotary engine is a type of engine that makes power with a spinning part instead of pistons. If the sealing inside the engine isn’t right, it can lose compression and run badly—sometimes triggering a safety/limp mode.
Compression is the engine’s ability to squeeze and pressurize the working space so the fuel can burn properly. If compression is low, the engine may run rough, stumble, and feel like it’s losing power.
Part
side seals
Side seals are small sealing parts inside a rotary engine that help keep pressure where it needs to be. If they don’t seal well, the engine can lose compression and start running rough after a short time.
Part
two new housings
In a rotary engine rebuild, the housings (the stationary parts the rotor works inside) must be in excellent condition because they form the sealing surfaces. Replacing housings suggests the rebuild addressed wear or damage that could otherwise prevent correct sealing and compression.
Part
sides resurfaced
Resurfacing means shaving or machining a surface to make it smooth and correctly shaped again. For an engine rebuild, that can help the internal parts seal properly so the engine can build compression.
Part
new seals
Seals are the engine’s leak-prevention parts. If they’re worn or installed incorrectly, the engine can lose compression and run badly, so replacing them is a common rebuild step.
Rings are parts inside the engine that help seal things up so compression stays where it belongs. New rings are often installed during a rebuild to help the engine run correctly again.
Limp mode is when the car intentionally reduces power to protect itself after it senses a problem. It can make the car run poorly or not move normally until the issue is cleared or the system resets.
The ECU is the car’s computer that controls things like fuel and engine behavior. If you swap it, it may need to be set up so it works with the car and its key.
Live data (real-time sensor readings) is information streamed from the car’s sensors to the diagnostic tool while the engine is running. It’s often used to confirm whether a suspected issue is actually happening right now.
Trouble codes are error messages your car’s computer saves when something goes wrong. A mechanic uses them to narrow down the problem before doing repairs.
A scanner is a diagnostic tool that plugs into the car and reads what the computer is reporting. It can show error codes and sometimes real-time sensor readings so you know what to fix.
A “custom tune” means changing the car’s computer settings. The goal is to make the engine run right and stop it from shutting down for the wrong reasons.
Mazda’s rotary engine is different from most car engines. Instead of pistons going up and down, it uses a spinning rotor to make power. Because it’s unique, some shops specialize in working on them.
Alcohol injection is an extra system that adds alcohol to help the engine run more safely under certain conditions. If you remove it, the computer may still be set up to expect it, so the car can run wrong or shut down unless it’s updated.
“Program that” means updating the car’s computer settings. If the car used to have alcohol injection but it’s been removed, the computer needs new settings so it can run correctly.
E15 is a type of gas that has extra alcohol (ethanol) mixed in—about 15% of the fuel. Some older cars don’t handle that alcohol blend as well, so people worry about compatibility.
Ethanol is a kind of alcohol that gets mixed into some gasoline. In older cars, it can cause problems because the fuel system materials and engine settings may not be made for it.
Concept
fuel blend compatibility limits in older cars
The segment describes how older vehicles may have limits on which fuel blends they can handle. Even if the engine computer can compensate at first, beyond a certain ethanol content the car can’t maintain proper combustion, leading to drivability issues and a check engine light.
Cars have computers that constantly make small adjustments while driving. If the fuel is different, the computer tries to compensate so the engine still runs correctly.
Running lean means the engine is getting relatively less fuel than it needs compared to the air. That can make the engine run poorly and can eventually trigger warnings.
Octane is basically a fuel quality rating related to how resistant the fuel is to knocking. A higher octane number can be good for certain engines, but it doesn’t necessarily mean the fuel has (or doesn’t have) ethanol.
The fuel pump is the part that sends gas from the tank to the engine. If it starts to fail—especially after many years—the engine may not get enough fuel.
A carburetor is an older-style device that mixes fuel and air for the engine. The point here is that different fuel-system designs have different durability and warranty concerns.
Fuel injection is how the engine gets fuel—using valves/injectors controlled by the vehicle. If the fuel system can’t deliver fuel properly, the truck can run poorly or not start.
Fuel injectors are the parts that deliver fuel to the engine. If they don’t work right, the engine can run rough or not get the right amount of fuel.
Term
E20
E20 is regular gasoline mixed with about 20% alcohol (ethanol). Some cars can handle that mix because their computer can adjust how much fuel they inject.
E30 is a BMW 3 Series from the older generation era. Here it’s mentioned because the host says it can run ethanol-blended fuel like E20 without issues.
The engine computer is the car’s “brain” for the engine. It watches sensors and changes things like fuel delivery so the engine runs smoothly with different fuels.
The Ford Flex is a large family vehicle with three rows of seats, made to carry people and cargo. It’s built more like a wagon/crossover than a traditional sedan, so it focuses on space. It may come up in a discussion about what kind of fuel or engine setup it has and how that changes ownership.
A flex-fuel vehicle is built to handle different fuel mixtures, like regular gas and a high-ethanol blend (E85). If a car isn’t set up for it, using that fuel can cause problems.
A flex-fuel car can use different fuel types, especially E85, which has a lot more ethanol than regular gas. The car is set up to adjust so it doesn’t run rough when you switch fuels.
If you put the wrong type of fuel in the wrong car, the engine can start running rough. Switching back to the correct fuel blend can make the car feel normal again quickly.
LIVE
Welcome to the Under the Hood Show podcast.
Thanks very much for listening and don't forget you can subscribe to our YouTube page
every week Thursday morning from 9 to 11 central and we do have some podcast sponsors.
Berkeley One Classics, Berkeley Classics is now Berkeley One Classics.
RoadReadyWheels.com and by car-parts.com now here is the Under the Hood Show podcast.
This is Under the Hood.
Welcome to the Under the Hood Show.
We are glad to have you with us.
Russ Evans is here to answer your automotive questions.
Thanks for joining us under the hood.
Shannon Nordstrom is not here to answer your automotive questions right now.
I am here to get your calls on the air.
I'm Chris Carter, 866-594-4150.
866-594-4150, that's the number to reach us here at the Under the Hood Show.
We've got one waiting on the line and he's been waiting for a little bit so let's get right to him.
Nathan is on the Under the Hood Show.
Nathan, what can we do for you?
Well, so I'll just get right into it.
I've got a 2008 Mazda RX-8 rotary engine, Winkle thing and my boy and I, I think this has been kind of a labor of love.
We tried rebuilding the motor, it had low compression, had it down at the Mazda dealership.
We got the sides resurfaced professionally, got two new housings for it, new rings, new seals, side seals, all that stuff.
It's got good compression again.
We started up, it runs for about 15 seconds perfectly.
Then it starts stumbling on itself and almost like it wants to go into limp mode and we can't even get it to drive.
It'll drive a first gear okay for a little bit and then you'll never get started again until you unhook the battery.
About 20 seconds, put it back on and it'll run just like that, start right up fine again and the check engine lights on all the time.
Only code I was getting was for an oil pump that we deleted.
We're putting mixed gas in it now, mixed gas oil and anyway, we put that back on just to make sure that the computer would see that we had the sensors and stuff there for it.
Still runs exactly the same.
I'm just wondering where to turn.
We did get a new ECU for it, a new used one for us and I can't find anybody to do programming for it or to swap it over to get the key to match.
I don't know where to turn.
I'm turning to you guys.
Nathan, hold on a second.
I'm going to reverse the order here on the Berkeley Classic.
I don't know if it would fall.
This one's iffy on whether it would fall on it.
This is a project car for you and your son, Nathan?
Yeah.
Hold on.
Instead of the color, I want us to guess who pushed this car as the project car.
Who saw this car? Who wanted this car as a project car?
I'm going to say it was Nathan.
I'm going to say they'd talked about it vaguely and then Nathan was like, this is the one we should get.
What do you think?
Probably was looking up on the internet and found it somewhere.
I'll bet it was.
I bet it was a kid that looked for the car.
I think the kid was going like, we should get a WRX and Nathan was like, how about this RX-8?
Nathan, whose idea was this car?
It was my son Ethan's idea.
Okay.
All right.
He was a senior in high school and he saw all kinds of YouTube videos on him.
All right. That's good.
I like this.
You bought in full?
We bought it used.
No, but I mean spiritually, you bought in new.
You bought in all the way.
Absolutely. I love the sound of them.
The weight, power distribution, all that stuff when they run.
That's such a good idea.
Boy, Nathan lucked out on this one too.
Because then you're going to go in all.
I like this.
This is good for Ethan.
So right now my son gave up on it and I'm basically the one that's full in yet.
So just throw that in there.
Did it run before you rebuilt it?
It did not.
We couldn't get it to start at all.
I wouldn't start at all.
Mazda dealership in Q-City and it was showing low compression.
Of course it takes one of those special.
Special electronic test area.
Correct.
Yeah. They're not even going to work on it.
Mazda dealers not even going to work on that car now.
They don't have any techs that do that anymore.
No.
I mean they'll change oil in it and stuff.
Change coolant, but they're spark plugs.
They're not going to.
They're like, no, we're not going to diagnose that.
It's just out of their wheelhouse because of the age.
I would cost them a lot of money.
There is a place in Dallas that specializes in rotary engines.
Okay.
I can't remember.
They might be on Forest Lane,
but look up Dallas,
Texas rotary engine specialists.
You'll find them.
You'll come across.
They got a Facebook page.
They got that.
I've been in there before.
They have everything.
They have everything for rotary engines.
They know every single thing about them.
There's nothing they don't know.
You'll have to pay them
because they do that for a living.
But they should be able to
help you out
with figuring some stuff out.
You're going to have to get a scanner
that can read data
as well as codes on that engine.
Okay.
If they can do it
without the car being there,
they're going to need to
some of that info.
You'll have to pay them over the phone.
You may end up traveling.
Where are you at?
What state are you in?
We're in the South Dakota.
Okay.
If you're down there,
to get to them,
you've got about an 11-hour drive.
You might even just make it a weekend project,
put it on a trailer,
haul it down there,
leave it, come back.
Because sometimes
that's cheaper.
I have people that come to us
from across the country
to have us do an engine in their car.
They've loaded them up, brought them here
from Oklahoma City, from Texas,
Georgia,
Colorado.
Wow, you're going a long way.
Don't you have a shop closer?
Yeah, I got one across the street.
Did I need to say anymore?
I'm like, okay.
Thanks.
But sometimes that's the easy way.
You find a specialist that can do it.
And it may be that because you've taken
the injection off
that car that you've got
a problem with it where the computer
is not recognizing it,
it's shutting the engine down.
Being that it starts and runs for 15 seconds
and then you can reset it,
that helps.
Because they'll be able to do,
they used to do custom programming.
I'm sure they'd still do.
But if they look at it
and they can fire up and see what's going on,
they may just go in there and custom tune it
and eliminate whatever's causing it
to not continue to run.
It's more than likely seeing a sensor
that has failed and it is
saying, hey, shut down
because something's not running right
and they can get it figured out.
Nathan, while we were talking,
did you Google it?
I've Googled
all kinds of things.
I don't even want to go to Google anymore.
I thought I heard you
Googling the typing
in the background there.
I'll tell you what.
Mazda rotary specialist in Dallas.
I did that rotary performance
in Garland, Texas.
That's it.
Yeah, rotary performance in Garland.
And then I put
Mazda rotary engine
expert near me.
You know, it came up.
You.
You're looking for that one because
it was in the city that I took you guys.
You and Shannon, we drove through there.
It's in Dallas Metro, but it's Garland.
The other nearest one to us was Tennessee.
Yeah.
That's the one you want to go to.
It's off of George Bush there in Garland.
But if he calls them,
there might be a way to work through it.
Well, no,
this is a good size shop.
Right.
But they specialize in a lot of custom stuff
because this is old.
They're going to want to put their hands on it
more than likely and fix it.
It may just be cheaper and faster
just to haul it, get it done,
be done with it.
And the conversation should start off
say, hey, I got a car
and it runs.
We've had it rebuilt, but it runs for 15 seconds
and shuts down.
So I have two choices here.
Would it be better for me to haul
this car to you across the country,
you know, 11 or 12 hours
and let you guys fix it?
Or
can I pay you guys
over the phone
to try a few things
before we have to haul it this way?
And they'll be like, oh, they're willing to pay me.
I'm willing to talk to them for a minute
because so many people just call
and say, I got these problems. Do you got a minute?
No, I don't have a minute. I've been working on cars
and every minute counts because
we're very short staffed.
So we want to get those cars done.
How would you, would you call them first
or send them a message first
if what should Nathan do?
Send them an email.
I understand you're a business.
Tell them what's going on and they'll appreciate that
and they'll be more willing to work with you that way
and
you know, just give them
short stuff. All you need to say is
look, this car didn't run when we got it.
We had it rebuilt for low compression.
Once we got it rebuilt, it runs for
15 seconds and shuts down.
So, yeah, and
tell them, you know, be specific. Say we took
the alcohol injection off of this car
and
we're, we bypassed that. So they may
oh, we may need to program that.
Does that help you out there, Nathan?
Yeah, at least give me
some return. I appreciate it. Just sitting out here
collecting bird stuff
and I don't want to see it getting
used. So I know his, his wedding's coming
up in about a month
and I kind of wanted it to happen for
his getaway, but
that was my hope.
So I'm trying to push it along here.
Thanks, Nathan.
Thanks very much for the call. Good luck.
866-594-4150.
That's the number to reach us here at the
end of the hood show. Let's talk to Matt.
You're on the end of the hood show. Matt, what can
we do for you?
Hi guys. Thanks for taking my call.
You bet. I just want you guys
to talk about
the new E15
gasoline that's coming out
and what are we going to do about
putting gas in our older vehicles
that don't like the ethanol
as far as the engine wear
and seal wear and things like that.
I'm just curious
what can we do
to keep driving our classic
cars, our older cars.
When you say older, what are you talking
about older?
Anything older.
Anything that doesn't run
doesn't like ethanol. E15
things like that.
I have a 2005 Chrysler
even old muscle cars
just all around older
older cars.
Well, 01 and up
which is almost
antique.
We're pushing almost 30 years
so the average age of the car
on the road right now is 12 years old.
So that means
if it's 20 years old
it's really old
and there's not many of those
and when you get older than that
I look at the shut cars that are in my shop right now
and the oldest one I've got in there is
2002
I think right now
and that's pretty standard for what we see
in the shop repairs.
So anything that's on our
lot basically will work
just fine on E15.
You start getting more than that
you can start having some weird things
going on. The computers
automatically adjust
and they'll adjust what they need to do
is put more fuel in
to get the same ratio out the tailpipe
because the alcohol content
makes them run leaner.
Once they get so far
the check engine light comes on
and that is when they're going to start running bad.
At that point you need
if you need to fix the problem
if it's an old one or newer
or you need to use a different
fuel one that contains
less than 15%.
Recently they
allowed E15 everywhere year
around as a waiver but
a lot of people don't know that
it's been around for
a couple decades now
and in the form of
something that I almost
consider it cheating because
they didn't say E15 on the pump
they just put this label on them
that most people have seen that says 88.
And 88
is the magic code word for
I contain 15% ethanol.
They settled on that
20 years ago and said
we're going to do that so people in Minnesota
that have told me
I've never used a drop of ethanol
in my car all I use is that 88 octane
because it's a little better than 87
I'm like
sorry you've been using E15 this whole time
how's it work? Oh I guess it works pretty good
that's fine
but now let's go older
lawnmowers
motorcycles
older motorcycles
cars older than
2001
you're fine for some of those but
if we really go back
carbureted cars
there's still some of those on the road
E15
is just a little
too lean
without jetting changes
in my opinion
if I've got a snowblower
that was made
old enough that it's from the early
90s it runs great
on 10
it runs
fantastic
on 0
just like a premium just no ethanol because
as I change from
0 to 10 to 15
it's running a little leaner
and when I run 15 in it
it won't idle well
it's you know loping it's
because it's lean if I put the choke on
just a little bit it runs perfect
well if I re-jet it it would run fine
on E15 or E10
but on nothing
it would be a little too rich and I'd be
maybe smoking a little bit
burning more fuel
that's the thing carbureted vehicles can't
adjust at all to that
pretty much
everything made
in the last
almost 20 years
they're designed alcohol resistant
because the manufacturers
that build the fuel pumps
and the carburetors on the small engines
they don't want warranty issues
and they know there's always a chance
that some is going to get in there at some point
so they want to try to make them
you know up resistant
as they can
but if you've got something old
if you've got a
1987
88, 89, 90 Chevy truck
with fuel injection
and you're running
15 in there more than likely
most of our customers are running it
they're having no problem
but
you know
it's already old the fuel pump may go out
and it may go out because
of an alcohol content issue
but it that pumps
probably over 20 years old
so it may have been time to change it anyways
and when you put the new one in it's going to be upgraded
and be alcohol resistant
but as far as like the injectors failing
and stuff like that I don't see that happening
in our shop
this 15 is going to be
pretty much standard
and once this is
I think it's stuck
I think now with the recent issues
we've had globally
and the fuel
I'll almost bet this is going to be a permanent fixture
and it will never go back to
a partial year thing
you'll see it all the time
no matter what administrations in there
once the cat's out of the bag
pretty much permanent and it's stuck a couple years
I think it's going to be here
but I think what you're going to see
is you're going to see the next step
they're going to start pushing towards E20
it's not going to be there all the time
it won't be year round
but you'll see pumps with E20
will that work?
I can tell you in my own car
and in Shannon's car
mine is
15 years old
and I've been running E30
in it for over 10 years
and I've had zero issues
it is not a flex fuel car
the computer is capable of adjusting
just fine
and a lot of other cars are too
it's not damaged anything
it's working fine
put 90,000 miles on it with zero issues
Shannon bought the brand new truck
that was not flex fuel and he's been running
is that 4 years old now Chris?
something like that? 4 or 5 years old
and zero issues with that
and I have a lot of customers doing it
I can't suggest anybody to use it
because it's not legal
to use in a non flex fuel vehicle
it's not certified for it, that's why it's not legal
don't know
maybe there is something that will happen
long term but we haven't seen it
and that's a lot of stuff to think about
but
for me on my own cars that are really
old
like 80's and older and lawn mowers
I'm still using
a pump without ethanol
because you can still pay for the premium
it's a lot of money
our biggest problem we're having right now
is people that
there are a few signs around
that say, at least in our area
that say it's okay to go low
that's been the
message on the sign
lowest price at the pump
that's the way to go, well the lowest price at the pump
is E85
do not put E85 in your car
if it's not a flex fuel car, don't do it
but they're doing it, I've had a few people come in
their cars ran horribly
and they're like, what do I do
and they had about a half tank of gas
and I said, let's go across the street
let's fill it up with non ethanol to the top
start it up, it'll probably clear right up
and all of them have, right away
but don't go
with the lowest price and put the E85
in there, it's not just not right
does that help you out there, Matt?
yeah, that worked out good
appreciate you guys, great show
thank you
we're getting to an age now
where 10
this question about 15
10 is everything basically
this question about 15 is the same thing
we went through with 10
in 2008
there are some concerns but for the most part
it's proven to be
a fine thing
right, yeah it's been
it's worked out
it's worked out just fine
they're doing some experimenting as they go
but yeah, I look to see
20
25 maybe, coming up
as the next thing
the E15 will just be
and it'll say 88 on the pump
or premium
or possibly 20
coming
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About this episode
A rotary RX-8 story kicks things off: after a low-compression rebuild, the car stumbles and seems to head into limp mode until the battery is disconnected. The hosts connect that kind of behavior to diagnostics, ECU programming, and why some Mazda dealers won’t touch older cars—pointing listeners to a Dallas rotary specialist. They also walk through remote troubleshooting with scanners and share practical guidance on ethanol fuels (E15/E20/E85), including why older cars may run poorly and what to do if the wrong fuel gets used.
We are the Authority in free Car Repair Advice. Call the Experts for your Auto Repair needs. We do it over the phone. We're like the friend you have that's a mechanic. A good one, but he doesn't really guarantee anything, but you really like his free advice. Call us and see if we can help you in some way. 98 Mazda Rotary won't run where to get help? Using Ethanol these days Saving on Gas Prices 80s Eprom Flashing 84 Chevy 6.2 Diesel won't shut off 91 Chevy Truck starter keeps going out properly shimming it Recalls on Recalls
