Rough idle on start-up, goes away in 30 sec

[Metallibird_Y87]

Hey guys,
2002 firebird, 60,000miles
Just after the warranty period on my car, wouldn't you know.
On a cold start, immediatly after start, were the car normally settles to an idle, it's started to "lope" severely for about 30 seconds. Like i had a wicked cam. If i rev it alittle bit it goes away sooner. Almost like a sensor needs to warm up or something. No codes
Does not do this if i start up after getting gas. sometimes does this slightly after work. I've ran a bottle of fuel injector cleaner to no avail.
Just bought the car, I don't think it has any mods except for K&N.
Otherwise, runs beautifully. got 33 miles to the gallon last week on the way to chicago. help?
MArcus

[vanbibber]

Re: Rough idle on start-up, goes away in 30 sec

not sure since its not throwing a code. it could be a few different things. you could have a vaccum leak.

funny you mention this becuase my 95 T/A does this from time to time when its hot out side, but not when its cold. no codes thrown either. ive tried replacing 02s and it didnt help and checked all the vaccum lines and everything else i can think of. all i know for sure is that it occurs when the car is running in open loop mode. try pulling the MAF off and cleaning it, it might be dirty due to the K&N filter and the oil that they put on them. which is a very common problem.

[Metallibird_Y87]

Re: Rough idle on start-up, goes away in 30 sec

ok, It just puzzles me because it only happens when cold. You would think that a dirty MAF would affect it all the time.
thanks for the reply.
Marcus

[vr4gasm]

Re: Rough idle on start-up, goes away in 30 sec

my g/fs camaro does the same thing 60K also it got real bad and actaully stalled out and therw a CEL for map or TPS but then it went away and just rough idle again

[Tech]

Re: Rough idle on start-up, goes away in 30 sec

I wouldn't worry about it my car is a 99 3.8 m5 with 107k and when I bought the car at 82k took it to the dealer to get a tune up and check up on everything. Passed the check list just fine. It's always had a rough idle for a minute or so then it clears up.

[CDNFB]

Re: Rough idle on start-up, goes away in 30 sec

I'll bet it has something to do with the emissions controls for the fuel tank vapor control. Try opening and closing the gas cap before you start the engine and see if that changes anything.

Hey BLLDOGG can you shed some light on this one?? Maybe I'm out to lunch on this one.

[BobbyZ72]

Re: Rough idle on start-up, goes away in 30 sec

There was a guy yesterday at my buddys shop with the same problem. The code said EMISSION CONTROL LEAK (SMALL) i left before he had a chance to look at it, but i will see him tomorrow and will ask what he found.

[Camarorulz]

Re: Rough idle on start-up, goes away in 30 sec

The fuel injectors are probably dirty. One bottle of the stuff probably isn't going to help. Run a couple of cans of seafoam (each with a full tank of gas) through and see if that helps. If it doesn't, have the injectors professionally cleaned or clean them yourself (if you know how.)

I had the exact same problem and it was dirty injectors.

[Metallibird_Y87]

Re: Rough idle on start-up, goes away in 30 sec

ok, thanks for the info guys, i'll try sea-foam

[vanbibber]

Re: Rough idle on start-up, goes away in 30 sec

i dont think its dirty injectors. my car has brand new injectors and its always done it.