CA Misfire & Lean condition

[suixo]

Bit of a problem here.

My CA is misfiring at idle, a lot.
When I start the car the AFR starts at 12, goes up to 18+, then back down to 14.6-15.
After that AFR is all good, almost doesn't move but I still hear and feel misfires.

When cruising at vacuum AFR shots up to 18+, can't accelerate unless I go deep throttle. Once I reach around 2.5 PSI of boost, car runs perfectly all the way to 14 PSI. Better than ever since I just changed the plugs and packs.

It's pretty much only misfiring under vacuum. Since full boost is fine, it can't be fuel or ignition or compression.

I'm at a loss as to what can the problem be. Any ideas?


I'm running a stage1 chip (already tried stock ECU, no change).

[jay1017]

Vaccum leak?


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[suixo]

I checked everything, I'd need a smoke machine which is really improbable to get here.

Anyways the problem is somewhat intermittent. Today lasted the longest but when I arrived home it didn't do it anymore. Right now the idle is still bad, but when driving in the garage in 1st gear the AFR stays around 15.
I've had this happen 2 or 3 times before, but it always went back to normal.

I could probably drive out of here fine, but after a while it will happen again.

[pointz]

Ecu temp sensor or lambda

You done diagnostics?

[suixo]

Unplugged lambda, no difference. Temp sensor? No idea, but how could that be the cause? I'll try to disconnect and see how it reacts.

I haven't checked the ECU codes, it's not really reliable lol.

[pointz]

Unplugged lambda, no difference. Temp sensor? No idea, but how could that be the cause? I'll try to disconnect and see how it reacts.

I haven't checked the ECU codes, it's not really reliable lol.

What's your afr on boost?

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[autosri]

Pressure test the whole system and see what leaks

[suixo]

AFR on boost is 10.4 - 10.7 at 13-14 PSI. A bit rich I think. But with the stock FPR and high boost it seems logical.

I do really need to test the entire air system. Either smoke or pressure or whatever. But it's a pain to find a way around here. If there's a leak it's hidden. Intercooler or even brake booster maybe.

Unplugging lambda makes no difference. Unplugging temp sensor did make the engine run smooth for 5 seconds, then started again. I'm going to change it later and see what happens. It's relatively new but it's not stock, so maybe readings are a bit off?
Also I discovered yesterday that my AAC is apparently shot. No difference whatsoever connected or disconnected (lights on/off, driving, etc).

And I was driving today, the AFR at vacuum was "ok" around 15.4 (at least not 18+). It appears the problem arrives when I drive hard. Although the idle roughness is now ever present (thought that is in part due to the bad AAC).


In a while I'm going to check ECU codes, change temp sensor and TPS because I put back an old one with a bad idle switch. Do some brake booster testing.

[suixo]

Twas the ETS! Glad it was that stupid and nothing major. Thanks pointz
Running better than ever!

[suixo]

NOT. Happened again a while ago. just during the drive to a place. Then went home perfectly ok.

This is insane. It's like sorcery.

[R3K1355]

Check the wiring then, could be a break or damage to a plug.

Lower loom can get rubbed through if the car runs too low.