Runs Rough

I have a 1991 Olds 98 - 3.8

Last week my harmonic balancer went out and broke the position censor. Just before this happened the car started running rough (dieing at stop signs, rough idle, ect...) I replaced the balancer and the censer and the car ran but still very rough. I then replaced the plugs and wires, air filter, and all the 1/4" rubber vacume hoses that I could see under the hood. Still rough. Tonight I replaced the fuel filter and reset the computer by un-hooking one of the bat terms and leaving the ignition in acc for 1/2 hr. (someone told me this is how you do it) The car is better but still rough at stop signs but hasn't died yet. Any suggestions? I bought a PVC valve for it but I couldn't find it under the hood.

Edit Update: I started pulling plug wires one at a time and found that with two of them OFF it made no difference in the idle. Is it running on 4? I pulled the plugs in question and they are sparking just fine. I am totally lost.

If you have two plugs that arent firing then trace them back to your coil packs. Rough idle definately sounds like bad coil packs.

While running the engine, use a pair of insulated pliers (rubber grips) and remove the plug wire from the coils one at a time. If one doesn't spark then you have to replace that coil pack.

The coil pack should run from $70-$150 (DO NOT use a Junkyard Special). Make sure you follow the wiring diagram that should come w/ the new pack (if they are the 3 pack assembly).

I believe the '91 and up 3.8 engines had separate coils so you would only have to replace the bad one...but all 3 at once would be best. Also, if you were running the car much on 4 cylnanders after you replaced the plugs, you may need to replace the two connected to the coil pack that wasn't firing right too...just check them to make sure they aren't bad.

As for the PVC valve, it is located on your manifold under a fuel rail by the plenum. Should have a L shaped rubber hose connected to it...you may need to replace the hose while your'e at it.

Good Luck and have fun :)

Thanks Alibi,

When I removed the plugs on the dead cylinders and tested them for spark I found that they have good spark. I'm getting spark on all six. Could it be clogged fule injectors on the two cylinders? I was told to run a can of BG 44K through in a full tank of gas.

Yes, it could be a clog in your injectors.

The only other thing i can think of is a bad Ignition control module (Located under the coil packs), however a bad ICM typically shuts the car down completely....

But....my brother''s car w/ a 3.8 in it had good coils, and a partially bad ICM....so if the injecter cleaner doesn't help then I'd suggest to try to pull the ICM and have it tested at Autozone or O'riely (free!).

If it tests good then the only other thing I could think of would be a weak fuel pump...

good luck. One more thing, if you still have problems, try to post in the olds 88 forum (more people visit, plus the cars are almost identical).