2003 GMC Sonoma Misfire

Hello,

So I have a 2003 Sonoma SLS 4.3L V6 with 166,000 miles and about a week ago it started idling really rough and then started throwing me a P0301 error code which I know means a cylinder 1 misfire, and I started smelling burning gas coming out of the tailpipe. So the first thing I did was change out all my spark plugs since it was about time to do so anyway.

The spark plug in cylinder 1 was black and burnt, but all of the other spark plugs looked fine. However, after I changed out all of the spark plugs now I get a P0300 multiple random misfire code instead of just the original P0301 code, and the original rough idling still exists.

I then replaced the cap and rotor and the cap did look pretty corroded, but the problem still remains. Also, I did check out all the spark plug wires with an inline spark plug tester and a volt meter for continuity and they were all fine and producing a consistent spark.

Now I am at the point where things get more difficult and more expensive and quite frankly I do not want to be just guessing and replacing items that are not the problem.

So any thoughts, or do you think it is probably a spider fuel injector problem?

One last thing, the truck seems to run fine when it is up to speed. I do not notice any lack of power at speed, it is only rough when idling.

Thanks,

Jerry