'92 3.1L Engine Problems

[Guest]

'92 gr. prix 3.1L

 

When my car starts cold, it's fine, runs like a champ. Half the time when I start it back up and it's already warmed up it runs like crap, sometimes so bad that it stalls. Pushing the throttle down does not help, though the problem will usually clear up in abolut 10 minutes. Sometimes it's so bad that it won't restart, it turns over gives me a couple chugs and stops. I have checked all of the injectors coil resistance and thy were in about a 1/10 of an ohm of each other, somthing like 12.3? can't recall...I have a brand new air filter, new spark plugs, a pretty new fuel filter and the ignition module and crank sensor were replaced less than 10,000 miles ago. I took the EGR valve apart and cleaned, it does the same stuff with or without it connected. I retrained the idle a few days ago and it didn't fix it either. Any ideas??

 

please help!

thanks!

Nick

[Guest]

oh yeah and I just rebuilt the motor about a month ago, so all the gaskets are new and *appear* to be sealing properly.

[Lee]

Maybe a dumb question but...Did you do the idle relearn for the computer? That'd be 1st thing.

[Guest]

yes, i did. the procedure i used was as follows:

 

dicsconnect battery for ~20 seconds

reconnect battery

run engine with trans in gear for 10 minutes

shut down for 20 seconds

run again for 5 minutes in gear

shut down

[stlunatics2oo3]

it could be your o2 sensor mine did something like that but it ran like real good or like 30 minutes and then stall and give 2 chugs and stall and not restart for awhile

[ctx46]

do you get any dummie lights? could be a map sensor... the one on my sisters GP did that exact same thing.....

[Guest TurboSedan]

have you checked the trouble codes stored in the ECM? this can be done by grounding ports A&B with a paperclip in the ALDL diagnostic plug under the dash. the codes can be read by watching the 'service engine soon' light on the instrument panel. a haynes manual will give you the procedure and has a list of codes. you've probably already done this, but anyway, just a thought.

joshua

[Guest]

no codes, no lights

 

would the 02 sensor pull a code if it was going out? and if I disconnect it when it's acting up shouldn't it default to the cold state? run really rich but run enough to know it's the problem?

 

would the map sensor pull a code too?

[crc]

yeah, they pretty much all spit out a code if something is wrong...

 

an o2 sensor gone bad is fairly easy to tell, lousy fuel consumption and sometimes a nice egg smell coming from your exhaust. Idle will yo-yo back and forth followed at times by complete shutoff.

[Guest]

im getting ~22mpg, the thing that makes me think it's not the 02 sensor is just that it will do it when the car is first started or keep it from starting. the 02 sensor isn't in closed loop until a few minutes after you start the car, right?

[crc]

yes, that's right..

 

but in your original message you said:

 

"When my car starts cold, it's fine, runs like a champ. Half the time when I start it back up and it's already warmed up it runs like crap, sometimes so bad that it stalls."

 

So which is it? Bad first starts or rough idle on restarts? I'm starting to think it is none of your sensors (which would throw a code anyway).

[Guest]

here's the question about the o2 sensor: does it kick on after say 3minutes, or is it when the engine hits some predetermined temperature?

 

I was under the impression that it was a sort of a time delay since we don't have a EGT sensor to tell the computer when the o2 sensor would be ready. If that is the case then it doesn't matter if it's warm or not, if it starts and runs like crap or won't start it wouldn't be the o2 sensor? I don't know.

 

I'm starting to think it's a vacuum leak so I ordered a mityvac from harborfreight to test the lines. There's a single vaccum line running to the FP regulator on the fuel rail and to the MAP sensor that seems like it could cause this. I'll post what I find out.

[crc]

here's the question about the o2 sensor: does it kick on after say 3minutes, or is it when the engine hits some predetermined temperature?

 

You should have a Closed Loop condition with engine temperature around 80c or 176F. The sensor though varies the voltage it reports to the ECM depending on o2 presence (obviously that's its function).

[Guest]

it's done it when it wasn't that hot. generally if it's warm and I shut it off, it will restart right away but if I let is sit for say 30 minutes so it can cool down a little, but not all the way, that's when it acts up.

[gpse3200]

'92 gr. prix 3.1L

 

When my car starts cold, it's fine, runs like a champ. Half the time when I start it back up and it's already warmed up it runs like crap, sometimes so bad that it stalls. Pushing the throttle down does not help, though the problem will usually clear up in abolut 10 minutes. Sometimes it's so bad that it won't restart, it turns over gives me a couple chugs and stops. I have checked all of the injectors coil resistance and thy were in about a 1/10 of an ohm of each other, somthing like 12.3? can't recall...I have a brand new air filter, new spark plugs, a pretty new fuel filter and the ignition module and crank sensor were replaced less than 10,000 miles ago. I took the EGR valve apart and cleaned, it does the same stuff with or without it connected. I retrained the idle a few days ago and it didn't fix it either. Any ideas??

 

please help!

thanks!

Nick

 

I'd check the Coolant temp sensor. Sounds like the somthing is causing the computer to throw in too much fuel, since you have to wait. You should try flooring it while starting, clear out the combustion chambers in clear flood mode, then release eventualy the motor should catch. If that sensor is slewed its gonna casue the car to do stupid things. Based on what you've told me, I thnk that its it. GM takes a long time before it will threow a code and something like this might not throw a code atall untill its gets totally out of range.