1996 Bonneville Misfire

My 1996 Bonneville SE recently started running very rough. The Check Engine code is P0303 - Misfire on Cylinder 3. I did a complete tune-up: Plugs, wires, pcv valve, fuel filter, air filter, and it still runs rough. Somebody in another thread (cbushnell) suggested that I look at the MAF sensor, because the car also hesitates when accelerating. I think they may be separate problems because the hesitation problem has been around for quite some time. The mis-fire problem makes the car run very poorly all the time. Whereas the hesitation problem had been very infrequent; now it has become chronic as well.

I checked www.obd-codes.com and they suggest a long list of suspects. Plugs and wires were top on the list because they are inexpensive. I'm going to reset the check engine light to see if it reports the same cylinder again. I find it hard to believe that any of the suspect sensors would consistently report the same cylinder. I'm guessing fuel injector, but how can I verify this?

What about the coil pack, could you swap with another pair to see if problem follows?

What about the coil pack, could you swap with another pair to see if problem follows?I thought about that, but the same coil serves cylinder 6 and cylinder 6 has 0 misfires. Seems like a bad coil would affect both cylinders, right?

A bad coil may or may not affect the other cylinder. I would have to believe that you have a bad injector on that cylinder. You have done everything that I would have suggested and since the problem is still there the only thing left is the injector. If you want to check it simply remove it from the suspect cylinder and replace it from one with no misfires. If the misfire moves then you have located the problem. Replace the injector and the engine should run properly.

What about the coil pack, could you swap with another pair to see if problem follows?
You were right! I switched the coils around and the codes changed to "Random Misfire". I just put on a new coil and the problem is solved. Of course, I probably fixed some other issues along the way, but there's nothing wrong with that. She's running good now!

Thanks for the help! $20 fixed the problem.

Glad to hear that you have resolved the problem.