Questions and Answers

Pontiac Grand Am #1 Cylinder Misfire Q. I have a 1996 Pontiac Grand Am 2.4 liter 4 cylinder engine which suddenly developed a rough idle, so rough the engine shakes at idle and a "putt putt" noise is heard from the exhaust pipe. Check Engine Light came on at the same time the rough idle started. A local auto supply read the code and said it was "#1 cylinder misfire".

I removed the Idle Air Control Valve electrical connection, then disconnected each electrical connection to each fuel injector, one at a time. Only the #1 cylinder did not reduce the rpm's. I replaced all four wire sets, no improvement. Replaced the fuel injector on #1 cylinder, no improvement.

Can you advise further diagnosis? Many thanks for the help - this is a great web site.

A. Wire sets?? This engine has no wires. Under the aluminum cover is a long plastic box with the ignition module and two coils inside. The plastic ignition "housing" is like a distributor cap and can develop cracks which can cause spark to jump to ground. I would replace this first. Also check the rubber boots and spring contacts for each cylinder. Any torn boots should be replaced!