Misfire if going above ~2500RPM (or into boost) when cold

[kainam00]

I've been having this problem since my last rally, and have had a hell of a time trying to diagnose it.

Anyway, when I first start the car, it will misfire badly if I give it any significant amount of throttle. It will rev up to about 2500RPM, then cut off right when the turbo starts spooling. Once it's up to operating temperature everything runs smooth as butter.

I thought it was the coolant temp sensor at first, but the resistance on that seems to be in the right range... so it should be ok.

Boost leak? The car runs perfectly fine when warm, so that doesn't make too much sense to me.

Plugs and wires are brand new.

Any ideas?

 

[crusher966]

What type of gas are you using? Whens the last time you checked your o2? When the o2 sensors are extremly bad or the car bottoms out on a rough surface it can cause this problem. I have only seen this twice but its worth a try. If this isnt the problem shoot me a pm and ill help you diagnose it.

 

[twister7]

Possibly a injector clogged! That happened to me not that bad how ever it was just tossing a code for cylinder 2 and idling ruff and shaking a bit!

 

[kainam00]

What type of gas are you using? Whens the last time you checked your o2? When the o2 sensors are extremly bad or the car bottoms out on a rough surface it can cause this problem. I have only seen this twice but its worth a try. If this isnt the problem shoot me a pm and ill help you diagnose it.

Running "Premium" gas, 93 octane.

Can you by chance point me to a procedure to diagnose the O2 sensors? Would a bad O2 sensor cause the car to run poorly only when cold, and run perfectly fine when warmed up?

Possibly a injector clogged! That happened to me not that bad how ever it was just tossing a code for cylinder 2 and idling ruff and shaking a bit!

Idle is fine unless I give it throttle when cold. Not throwing any codes.

Keep 'em coming guys!

 

[twister7]

Running "Premium" gas, 93 octane.

Can you by chance point me to a procedure to diagnose the O2 sensors? Would a bad O2 sensor cause the car to run poorly only when cold, and run perfectly fine when warmed up?


Idle is fine unless I give it throttle when cold. Not throwing any codes.

Keep 'em coming guys!

car is in open loop not using the o2 at all until it is up to temp, not the problem!O2's come one line at about 160-180 range

91's are obd1 i don't think they even have miss-fire codes clean the injectors out any ways ,when i said idle ruff i mean hardly noticeable in my case!

Check fuel pressure, some time's when a pump is getting weak u will have issues when it first starts up cause the motor is need more fuel until warm!

Give me more details, like how warm and how cold, does it do this ever single time?

 

[kainam00]

It does it every single time, and will do it until the temp gauge is about 1/3 of the way up, which is usually where normal operating temperature is for this car.

 

[my4ATEurV8]

a lot of peaple overlook spark plugs. check the gap. a few years ago mine would misfire when i got over 12-14psi on a 14b. turned out i forgot to gap the plugs when i bought them.

 

[kainam00]

What should the normal gap be? (DSM newb here again

I'm pretty sure they are properly gapped (as they are NGK stockers, never had to gap those before), but I can double check.

 

[twister7]

What should the normal gap be? (DSM newb here again

I'm pretty sure they are properly gapped (as they are NGK stockers, never had to gap those before), but I can double check.

vin R&U .28-.31

 

[kainam00]

I think I've fixed the issue. For shits and giggles, put Sea Foam in the gas tank and intake. After a whole lot of smoke, and waiting about 3 hours for the engine to cool back down, the problem seems to have gone away. The engine seems to be running a whole lot smoother in general.

Assuming that it does not come back, I'm thinking it was probably something fuel related. I did get a nasty misfire going up hills at the rally, so maybe some water/dirt got into the fuel or something?

 

[twister7]

I think i would send those injectors out to be cleaned or stick a set in that has been one stopped up injector could equal one fried piston......been there done that..it sucks!

 

[knochgoon24]

You may want to change the fuel filter.