My 92 SSEI idles rough only when it warms up but it is sporadic. I took to gm Dealer and had them perform injector balance test and fuel pressure test. They said nothing wrong with engine. I looked at printout data from test and everything looks normal. Morons tried to sell me new engine and transmisson mounts for $1300. and said that causes engine to idle rough.

Anyway I replace three coil packs (they were cracked) and wires and IAC and cleaned throttle body new 02 sensor as well . No change this problem started and three years ago and is now getting worse. Tach shows steady RPM, never stalls, Motor runs fine in every other sense, even great gas milage 36 Mpg on hwy 70 mph lots of power. Car has 340,000 Kms but runs great other than this annoyance.

Dealer is useless I am not wanting to perform shotgun mechanics "too Expensive" for that guessing game.

anyone have similar problem Cure??

Well if its only when its warming up then its not your o2 sensor, its ignored until its warm. I had a similar problem when I would first start my car after its been sitting for a while I'd get a really rough idle. Holding the rpm'* up to 1500+ for about 30-40secs and letting off would cure it and I wouldn't see it again until I let it cool down and tried restarting it. Sound like your problem? I dunno how much help I am because as you can see in my sig I don't think I could tell you exactly which part fixed it. For the 2 days I had my car I never experienced it so I would think the problem is gone. Since it is aparently temporary I would rule out your ignition system and go more towards one of the sensors. Actually I would look at your MAF sensor, and this is why...When its starting up if the MAF sensor is sending bad data the computer can't use the O2 sensor to compensate because its forced to ignore it so the only choice it has is to run rough until it can verify data from the o2. Once it warms up and starts reading the o2 sensor it may realize that it is running rich/lean and compensate which would result in the engine running better once its warm. Clean your maf sensor! Pull your MAF sensor from it is housing which only takes 3 screws. Go get some good cleaner that is safe for sensors like maybe electronic cleaner or brake cleaner. I've read a lot about using brake cleaner so thats probably what I'd use. Get the cap off a 20oz bottle and if so equipped use the little red straw that'll sometimes come on the aerosol can. Aim it at the 20oz bottle cap and VEEEEEERRRRRYYYYY lightly spray some in the cap. You wanna try and get it to dribble out. I've never done this with brake cleaner but I have with other fast evaporating products and it might take a minute of practice but it should be possible to get a small amount in the cap. If its not working right and evaporating too fast use the 20oz bottle you took the cap from and spray like a madman inside it until you get some liquid at the bottom. Either way use this to pour ever so lightly onto the wires on the MAF sensor. Pour from one side then wait and pour from the other side. Let it stand about 5-10min because its probably got ice on it now. Re-install and start the engine. I'd bet $10 this'll fix a lot of the rough idle.

35mpg....thats insane...i dont think factory specs give it that much...