IAC or Dirty Injectors??

[cles]

The past couple of days, my car has become difficult to start when warm. If I usually have to give it some gas to get it started. If it does start without pressing the pedal, it idles rough at around 700 rpm for a few seconds, then revs up to about 2000 for a couple of seconds, then back down to 700. The idle is rough and a little black smoke is coming out the exhaust. It runs fine at anything above idle.

 

I'm thinking dirty IAC or injectors?? By the way, the car is a 1996 GTP with a 3.4L.

[mfewtrail]

Those symptoms are also fairly consistent with what you would have if the fuel pressure regulator fails...pull off the vac line from the FPR to the throttle body and check for gas. You stated you have a bit of black smoke out the exhaust..this indicates a rich condition.

[Brett H]

I have exactly the same problem that you stated. I've been chasing this problem without success and its the reason I found and joined this board, so I can get some help.

First I can tell you it isn't the IAC. I swapped mine thinking that was the problem but nothing changed.

I thought it may have been a plenum gasket leak but not likely since it only happened once it was warm. I did the old propane torch around the intake trick but the idle never increased so I ruled it out.

My problem is intermittant. It only happens after the car is warm but not always. Sometimes while I'm driving and come to a stop it idles rough and if I turn the car off then restart it shortly after, it has a hard time starting then revs high for a bit.

Because the problem is not consistant and I have begun to get an engine light the past couple of days my suspicions are that the problem may be a bad O2.

I hope you figure out the problem and if you do let me know, I'm tired of chasing my tail on this.

BTW: The car I'm referring to is a 94 Cutlass Supreme with a 3.1

[GP1138]

Try running some injector cleaner through it to see if that helps at all. If you've got black smoke, I'm not sure though.

 

Pull the brake booster line, and run a can of Seafoam through that vaccuum line. It should clear out any deposits that are clogging up your intake. It's fun to do, too, to see all that smoke everywhere.

[sdwhite]

Yup. I'd be dollars to doughnuts that it's the fuel pressure regulator. I had the same problem and replaced darn near every sensor on the thing.