So I have a question for you guys. I have an 04 rx8 and it is reading a misfire code. I took it to a well known mechanic in my town and he ran compression tests and checked the sparkplugs, coils, and cat. He said everything seems really good but the comp is still reading a misfire. What could be the issue? Should I get a new ecu? Please let me know and I value your feedback. Thanks

 

There is a 99.5% chance the ECU is correct, and your mechanic is wrong.

Here is a thread that covers troubleshooting misfires:

https://www.rx8club.com/series-i-tec...t-here-222280/

It is good to do everything in that thread as part of regular maintenance, however it usually comes down to the ignition system.

Replace the coils, wires, and plugs as a unit and clear the codes. The entire ignition system is considered wearable on this car, and it should be replaced no less than every 30K miles--sooner if don't know how old it is or if it shows any signs of weakness. If you shop smartly, you can buy all the parts for around $150.

 

+1^
If you have any mechanical aptitude and a few specific tools, can do most maintenance and repairs yourself.
They're pretty easy to work on, and this forum has all the DIY and Troubleshooting info you need.

 

Is it a well known rotary mechanic? Or someone who works on many cars but few rotaries? They are not the same animal

 

He works on a lit of rotarys and he works on piston engines too. I really am confident in what he told me. He is well known and very well rated.

 

It's funny that he's wrong then.

 

I really don't think he is wrong.

 

Did it have a CEL, how did you find out about a misfire code?

 

Yes the light comes on and then goes away after a while then comes back on and then off again. It doesn't stay on and it doesn't stay off

 

That's an interesting opinion, because he is.

 

Do you have the actual codes?
I've been on this forum nearly 4 years,
I've read about problems nearly every day since then, and I don't think I've ever heard of a recurring CEL that was a ghost in the machine.
Your's would be the first.

If your coils, wires, and plugs have not been changed in 30k miles, then it should be done.
If you have had CELs popping up for an extended time, and it is misfires, your cat could be damaged.

The ignition components can be replaced, but if the cat is damaged, it can cause misfires as a result.
It should be dropped and visually inspected.

Misfires kill cats, bad cats kill engines.

In your first post you said you value our feedback, but you insist your mechanic is right.
If we're right, changing the ignition will cost a couple hundred bucks, and maybe if your cat isn't already bad, that will solve your problem.

If your mechanic is wrong, it'll cost you a couple of thousand at best.

Your call.

 

You said he's worked on rotaries. Which is fine. If he hasn't worked on a slew of RX8's and their almost FIAT like amounts of weird issues.... then he may not be familiar with what this last generation engine likes and doesn't like. I'm with BC on this one. My car came to me with an odd misfire that cleared up with new coils.

 

Good point.
That's why I'm asking for specific codes.
I may be presuming a bit much.
It's possible it's not ignition, but I think those are the usual causes of misfires.

The mechanic can't find any issues and is blaming the ECU.
Have you experienced this?
I'm only going by what I read on the forums.

 

I had misfires at high RPM when I had a slight coolant leak into the combustion chamber on my last Mazda reman. I would get the blinking CEL indicating a misfire, but no stored codes.

 

I used to get an occasional flashing CEL and no code, but it didn't happen often, and it's been a couple of years.

He did say he had misfire codes.

 

Ah I didn't read the first post, just the post where he said the light would come on but not stay on. Still, as Charles said, there are abagillion things that can cause a misfire.

http://foxed.ca/rx7manual/2003mazdar..._S01_0016.html

 

See and that's what I'm saying. There could be so many things that can cause a misfire that we can't be 100% sure that my mechanic is wrong. I'm just going to take it to Mazda and gave them check it out because we have tried everything. We checked the plugs, coils, cat, compression and it is all perfectly fine. This CEL is bugging the **** out of me

 

But how do you know that? I mean there are so many things that could be wrong. You haven't looked at my car and your not in my position.

 

I do value what you guys have to say. I'm just trying to get an answer of what's wrong. I cannot feel it misfire and I've had the cat checked 2 times and its all good. Litterally last week on Friday I had them check it and its perfectly fine. So your saying I should try to change my ignition and see where that gets me? Cuz honestly its bugging the **** out of me and I'm seeing where you guys are coming from. He probably is wrong. I've never heard about this problem either. Its got 57,000 miles and I'm not sure if the previous owner changed anything on it. I'll check it out. Thanks

 

Okay, when you say you had the cat checked, how exactly was it checked?

 

I once had missfire codes/flashing cel after swapping another engine into my car. The newer engine ran great, but the cel would randomly flash with missfire trouble codes, but no missfire ever happened. I was confused, all ignition was new, car ran great. So, I did that 20 brake stomp thing and haven't had a flashing cel since.
Clean the ess and do the 20 brake stomp reset, and report back. Try it, it is free easy and takes little time and will eliminate one of many possible reasons for flashing cel.

 

This is a commonly missed step when installing a new engine.

 

I just had issues getting home with I believeca faulty pump.
At one point I revved the crap out of it and took off, got a brief flashing CEL, ( first one in years) and a P0302 misfire code.
But it was popping and stalling beaucoup times.

 

Popping in the exhaust would be extra fuel, so possibly ignition failure. Not saying it's not the fuel pump, but a fuel pump problem would not result in extra fuel.

 

Well, if it is, then SakeBomb got some splainin to do.