Code 305, Cylinder 5 misfire

[stanleyb1951]

My 1996 Bonneville SSE sets code 305 (Cylinder 5 Misfire) Changed spark plugs and HV cables. If I erase the code using my scanning tool it lasts 3 - 5 days and the code is back. Car has 39000 Miles. I think if the coil is bad I should get not one but two cylinders misfire, since the some coil serves two cylinders, is this logical?. Did any one ever experience this problem? Any help will be greatly appreciated. Thanks.

[markwb]

Can't answer the question really, but suppose you were to interchange the suspected faulty coil with another one & check to see if the problem follows or stays at cyl. 5 misfire.

[jselnekovic]

I have a 97 Bonneville SE with a P0303 (cyl 3 misfire). I started off changing my plugs and wires, but that didn't solve the problem. Then I swapped in a new coil pack for cyl. 3/6 and that didn't help either (along the way I learned that half of a coil pack can go bad). Next I replaced the Ignition Control Module, but I still have the problem.

Trying 2 sets of plugs, 2 sets of wires, 2 coil packs and 2 ignition control modules hasn't solved the problem. Anyone have an idea what I should look at next? I'm thinking wires and connectors maybe.

[stanleyb51]

Is your code 303 staying on, or is it intermittent?

[jselnekovic]

Each time I disconnect battery or reset the code, it takes about 20 miles for the light to start flashing. After that the code the light is on solid. I think it resets itself after approx 8 hours though.

[ro25]

i had the same problem i figured out that cylinder 5 was not fireing at all by removing the spark plug and placing it on a ground and looking for a spark while i started car. it wasnt sparking so i switch 2 off the coils to see if it was the problem sure enough 5 was sparking so i replaced the 2-5 coil and the problem was solved... after about 2 months though my ignition module went, some say it was because of the faulty coil? i dont know.. maybe coincidence.

[Flatrater]

Not all misfires are caused by spark. Don't forget you need fuel too. No fuel or too much fuel you get a misfire.