CEL = Misfire??

[100_Percent_Juice]

As some of you may know we installed the vf34 combo on my friends 02wrx a few weeks ago. Since then he has had the new clutch installed and needless to say the thing runs like a champ. The engine light came on probably 15min after we first did the install and we just figured it was an uppipe cel. Anyways the place who did his clutch tested the cel and said it was reading "engine misfire". Personally I dont exactly know what that means because it runs so smooth and awesome. Could this be a false error code? Could the AP map be throwing this CEL? Any info on this would be awesome so he doesnt have to take it back into the shop and spend a ton of money for them to find the problem. Oh and he would have posted this but he has been out of town.
Mods list:
vf34
complete catless TBE
catless UP
pinks
walbro
Cobb AP vf34 map
Exedy Organic
light flywheel

[Kevin M]

Light flywheels often cause bogus misfire codes if you're not exceptionally smooth with it at low engine speeds.

[The Chef]

Originally Posted by BAN SUVS

Light flywheels often cause bogus misfire codes if you're not exceptionally smooth with it at low engine speeds.

That would make more sense. A misfire on that car seems so ridiculous cuz that car runs smoother than my stocker

[Kevin M]

Also, I don't see spark plugs on that mod list. Make sure they are new and properly gapped, they can contribute to it.

[sperry]

Originally Posted by BAN SUVS

Also, I don't see spark plugs on that mod list. Make sure they are new and properly gapped, they can contribute to it.

I don't think the plug will make a difference... if it's a false misfire (lightened crank pulley or flywheel allows the crank and cam sensors to get out of sync enough the ECU thinks there's a misfire). If the plugs make a difference, it's a real misfire.

[Kevin M]

Originally Posted by sperry

I don't think the plug will make a difference... if it's a false misfire (lightened crank pulley or flywheel allows the crank and cam sensors to get out of sync enough the ECU thinks there's a misfire). If the plugs make a difference, it's a real misfire.

Yes... correct. CEL either way...

[Dean]

I thought he just did a new clutch plate. Did he do a flywheel as well?

[100_Percent_Juice]

Yeah he got the clutch/flywheel combo.

[100_Percent_Juice]

Originally Posted by sperry

I don't think the plug will make a difference... if it's a false misfire (lightened crank pulley or flywheel allows the crank and cam sensors to get out of sync enough the ECU thinks there's a misfire).

So if he were to take it to a place (GST) and get it tuned, could that be fixed with the tune? Or is that even a real problem that the ecu "thinks" there is a misfire?

[100_Percent_Juice]

Someone posted this on nasioc "sounds like you have a leak somewhere between the maf and the turbo... also check your coils and spark plugs.... but my guess is a vaccum leak letting in extra unmetered air....."

Could this cause it? When we installed the turbo there was a small rip in the inlet hose coming to the turbo. I was pretty sure that we got that all sealed but if that was a small leak do you think it could cause this?

[Kevin M]

A vacuum leak, even minor, should cause weird issues that you would notice other than with just the CEL.

The flywheel triggers the misfire because with the reduced mass, you can have faster changes in engine speed, whether from lift throttle or engaging the clutch with insufficient throttle. Both of my RSes did it some of the time if I was driving at all like a noob. My OBS doesn't though.
Mike may be able to remove the trigger values through tuning, but I don't know. Ask him about it, he may have a fix for you.

[100_Percent_Juice]

Ok everyone, another question reguarding the same problem. Loren thinks that one of the injectors could be loose or not pushed in all the way. I installed them and I told him that I pushed them in as hard as I could and that there is no way one is loose. He thinks that is the cause of the CEL on his car, I think that would cause much bigger problems. What do YOU think about that?

[sperry]

Originally Posted by 100_Percent_Juice

Ok everyone, another question reguarding the same problem. Loren thinks that one of the injectors could be loose or not pushed in all the way. I installed them and I told him that I pushed them in as hard as I could and that there is no way one is loose. He thinks that is the cause of the CEL on his car, I think that would cause much bigger problems. What do YOU think about that?

No fuel, or no signal to an injector will certainly = misfire... but the car would be obviously off-song, even at idle. Don't ask me how I know.

[100_Percent_Juice]

^Im basically looking for someone to rule that out, I mean the car idles and runs like a champ and you never feel any hesitation or anything, tt never even afterfires or anything, so personally I dont think the problem lies with the injector install. Someone make me feel better and agree with me...please?

[sperry]

Originally Posted by 100_Percent_Juice

^Im basically looking for someone to rule that out, I mean the car idles and runs like a champ and you never feel any hesitation or anything, tt never even afterfires or anything, so personally I dont think the problem lies with the injector install. Someone make me feel better and agree with me...please?

Here's how to rule it out... with the car parked and idling, pull the signal line to each of the injectors, one at a time. If you pull one and the motor doesn't suddenly sound like crap, then that one wasn't working to begin with.

...though, you should be able to tell if the motor's running on 3 cylinders to begin with, just by listening.

[100_Percent_Juice]

yeah it sounds great, he has the GP moto exhaust from BOO. Plus it has awesome powaH, on the freeway he pulls away from my car like a stock sti.

[Dean]

As far as a loose injector... If you are leaking air around an injector, then it wouldn't be the same as if the plug was disconnected. Not sure it would cause a misfire, more likely a lean condition and knocking unless the leak was massive at which point I don't think it would idle well as the misfire would be nearly continuous...

[100_Percent_Juice]

Dean, maybe i can have loren come with me to your house and you can drive his car.

[MPREZIV]

The problem with misfire codes, is that if the ECU notices that there's a cylinder that's weak, but not even completely dead, it can throw a misfire code. Ass-dyno wise, you can't really feel anything wrong, but the ECU sees a difference in the cylinder output levels, (something you could see on an o-scope, which has unfortunately gone the way of the carburetor and the Dodo...).

Is the code just a P0300, (random misfire) or is it a P030(1,2,3,or 4) indicating a specific cylinder?

[100_Percent_Juice]

I dont know which one it is, i will have to ask, I just know that the CEL is blinking all the damn time for him.

We are actually headed to the dealer today to get some replacement parts. Does anyone here have a stock turbo inlet hose for sale? If not does anyone have an aftermarket one?

[sperry]

Originally Posted by 100_Percent_Juice

I dont know which one it is, i will have to ask, I just know that the CEL is blinking all the damn time for him.

We are actually headed to the dealer today to get some replacement parts. Does anyone here have a stock turbo inlet hose for sale? If not does anyone have an aftermarket one?

Yes, and yes. But I'd have to find them and see what condition they're in.

[100_Percent_Juice]

Please do^ after all those parts the wallet is getting skinny.

[MPREZIV]

Originally Posted by 100_Percent_Juice

I dont know which one it is, i will have to ask, I just know that the CEL is blinking all the damn time for him.

We are actually headed to the dealer today to get some replacement parts. Does anyone here have a stock turbo inlet hose for sale? If not does anyone have an aftermarket one?

It'll help to find out EXACTLY what code is thrown. If it's a 300, then there is likely a common cause making the engine "random" misfire. If it's a 30X (123 or 4) then you can look into fuel injectors/coils/plugs/compression for that particular cylinder. The blinking CEL means "catalyst damage possible", i.e. too much fuel being unburnt going through the cat., from a misfire. [Just in case you didn't know why it blinks...]

[100_Percent_Juice]

Another thing, he has a BOV and a full catless exhaust which should mean that if there is that much extra fuel coming through, we should see a flame. I will get the exact code from him tonight. Dean said there is a website that I can input the code? Does anyone have a link for this?

thanks

[MikeK]

There is a sticky on nasioc somewhere with the subaru specific list