Misfire code when not actually misfiring
#1
Misfire code when not actually misfiring
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
#2
Water Foul
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.
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.
Last edited by Steve Dallas; 11-15-2016 at 07:56 AM.
#3
You gonna eat that?
iTrader: (1)
+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.
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.
#5
#8
You gonna eat that?
iTrader: (1)
Did it have a CEL, how did you find out about a misfire code?
#9
#11
You gonna eat that?
iTrader: (1)
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.
#12
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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.
#13
You gonna eat that?
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There are about a dozen reasons for misfire codes, according to the Mazda FSM, but I will need to look them all up later and post them as I must head out for a few. For starters, we have poorly firing fuel injectors, low oil pressure, low compression, low fuel pressure, and several others.
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.
#14
SARX Legend
iTrader: (46)
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.
#15
You gonna eat that?
iTrader: (1)
He did say he had misfire codes.
#16
SARX Legend
iTrader: (46)
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
http://foxed.ca/rx7manual/2003mazdar..._S01_0016.html
#17
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
http://foxed.ca/rx7manual/2003mazdar..._S01_0016.html
#18
#19
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.
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.
#21
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.
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.
#22
SARX Legend
iTrader: (46)
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.
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.
#23
You gonna eat that?
iTrader: (1)
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.
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.
#25
You gonna eat that?
iTrader: (1)