I'm getting an OBD code P0301 on my '04 3800 ss. It's been going on for probably 2 months now. I changed the plugs and wires and cleared the code, but it came back the next day. The people at O'Rileys suggested that I change my coil pack, but since the pack supports 2 cylinders, shouldn't I have codes for 2 cylinders? O'Rileys suggested that I swap the coil pack on the cylinder that's giving me problems with one of the others and see if the code changes. Any other suggestions on what I might do??

 

Do what oreillys suggested that way you know its the pack

 

If the coil pack was malfunctioning then you should be seeing a misfire on cyl #4 also, but it won't cost you anything except a little time to swap it with another coil pack to verify it isn't the problem. I'd pull #1 plug and examine it. If it shows signs of being rich I'd swap a couple of the plug wires around and see if the misfire follows the wire. If it does replace the wire. If not, replace the plug. If the plug shows signs of running lean I'd run a tank full of gas with some fuel injector cleaner in it and see if that clears up the problem. If not, check the voltage to the injector. If it checks out okay then replace the injector.

 

Okay i switched the coil packs, and the plug and wires are brand new. Drove a few miles and got the misfire code again. I've already tried a fuel system cleanser and the problem is still there. Gonna check out the injector tomorrow. Thanks for the help!

 

I have seen were something damaged only one of the two towers on a coil, causing one cylinder to misfire. The advice Oreily's gave of trade that pack with another one and see if the problem follows the pack is sound. If you mis-fire magically moves, you found the problem.

ALso, what brand plugs did you put in? AC Delcos are the best, but if you say BOSCH, my advice, rip them out NOW. My experience with mutiple GM modern v6 engines and BOSCH is:
- One out of 6 is sometimes faulty
- If you get a good set of 6 plugs, about 6 months later the car mis-fire a TON

Back to your problem, pending you don't have BOSCH plugs and the problem does not change cylinders swapping the coil pack, next guess is fuel injector. I have heard of some people trading injectors on the fuel rail to pin point a bad injector. FYI - Usually when you are having a problem (such as a failing injector), fuel cleaner will not resolve the issue.

 

I assume it was the same code - #1 misfire? What did the plug look like? Even though the wires are new it's possible you got a defective one.