Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show



I have a 2004 Cadillac it started to miss when your idling, a check engine light when on and it was #5 plug not firing so I changed the plugs in front 4 of them and also bought a coil pack and replaced that, but it still misses. What else can I check before thinking its a sticky Valve or internal engine problems. Any Idea’s would help.

Thank You


Number 5 cylinder is third on rear bank. Replace the rest of the plugs and see what happens.

All the plugs were changed at 100,000 miles and I have 106,000 now. After changing the coil pack it still missed so just for the heck of it I changed the front 4 plugs again…I would think its not the Plugs…Just a guess…

Any other suggestions

Thanks Chris

First I have to assume that you got a P0305 code. That doesn’t specifically mean that the plug isn’t firing. Its really just about that cylinder. Each cylinder needs 4 things: spark, fuel, air, compression. And it needs them all in the right timing.

You didn’t mention it but I assume that you also replaced the wires?

The next thing you should do is check the compression before you end up chasing your tail for nothing. If the compression is good I’d inspect the injector wiring and then swap the #5 fuel injector with another.

Yes Sir you are correct (cylinder not firing) and yes the coil pack assembly comes complete with wires…So next thing I will try is the compression…good idea. If the compression is good, I will check injector.

Thank You

If the plugs dont cure it the next item is wires…But if Pete is correct you are going to need to jack up the car and get on your back to reach those rear plugs I believe. Sometimes that is the best way to get to those hidden plugs.

I did change the rear plugs at 100,000 miles it now has 106,000…and reads a code the #5 cylinder is not firing properly…so I don’t believe its the rear plugs or wires.

Thank You