I have developed a bad st-st-st-stuttering problem. It used to be only once in a while but now its as soon as the car is started. 98 cavalier 2.2L 5spd manual. I have replaced the plugs and wires, TPS, front O2, IAT sensor and ran seafoam thru it. I get a strong gas smell as well from the exhaust. Ive read that the coil packs might be the cause, ive heard the rear O2 sensor could do it along with the MAP and EGR sensors or a vaccum leak somewhere over the rainbow. I have already bought a 2005 cavalier to replace this as my daily driver but I would love to get this fixed since its a 5spd 2 door instead of my new automatic 4dr "family" car. so far i have gotten no codes. the last code i got was engine too lean (P0171) and that hasnt come back since the front O2 was replaced since I got a HO2S insufficient switching (P1133). previous codes in the past were the TPS voltage low and engine too lean and too rich (P0171 and 0172) at the same time. havent seen all them together since replacement TPS was installed. Could a bad ground to the battery or chassis cause any of this? I did notice the terminals were kinda dull. I am going to clean them tonight and brush them up real nice. Let me know what you guys think.

Sounds like a coilpack or IAC. Could be a million things though.

any easy way to see if the coil packs went back? is that as simple as pulling the plug wire off and watching for the spark? and also, to just make sure i understand correctly that cylinder 1 and 4 share a pack and 2/ 3 share the other. or should i take it to a ma and pa shop and let them tell me whats wrong for $75? i am sure they have more time to play with it than me.

Pull one wire off a plug at a time. If one of the CPs isn't sparking you'll find it. Pull one at a time, and compare results.
Engine continues to chug with any one of the four off: Not the CP.
Engine dies when you pull a certain wire, not that wire.
Engine dies when you pull any of the other three wires, but not this one: CP, Wire, or Spark plug is probably bad. Could also be the ICM.

GMs four bangers can't run with two cylinders off, so you can eliminate good cylinders by this method.

Don't hold the wire while the engine is running either. You'll be amazed at how far that spark can jump, and you don't want to be the closest thing to jump to.