1988 Buick Park Avenue 3.8L 114,000 miles. Never let me down.

Rough idle. Changed spark plugs and wires. Started car and sounded and idles way better. Drove about a block away and idle started getting rough again. I did get back about half the power and its not idling as bad as before. Still I'm not satisfied. Should I check out the coil box. The 1.2 mile drive to work the service engine soon light would come on. When I got close to work it would turn off. This 3.8 been a great motor just like the 1992 Century. They are great engines. It's definitely not the prettiest car cosmetically.Outside is oxidized. I wasn't going to buy it till I looked under the hood. With such low miles, smogged and registered, I don't want to give up so soon. It has never let me down.

First thing that I would do is buy one of these spark testers?

Buy at least one and put it on the coil tower where the spark plug wire goes and the spark plug wire on the top of the tester. If the car will continue to run for five minutes and no misses, then the coil is good. If not, then it is not good. Need to replacement. You only need to do one coil tower/ coil. Not necessary to do the coil on both towers. Just move down the line and do the other two coils.

Also, be sure to check the grounds especially the one below the coil.

Might also be a bad ECM but generally not in your model year. Easy base line check for that is to LIGHTLY TAP on the ECM with the engine running and if the engine stalls, hesitates would be an ECM issue.

Pull plug wire from coil, 1 at a time. See if it misses. If miss does not change, may be coil. But on mine , it was the ignition control module, directly beneath the coils. Pull it and take to your favorite parts store. They can check.

Ben

Can you tell where ECM is located? I have one on the way. Any advise on completing the installation would help too. I miss driving this car. Thank you.