Misfire on cyl. #1

[GPFred]

I have a question(s) related to misfire. I have a 2000 GP with a 3.1 with about 110K on it. I have researched the threads and will follow a plan to hopefully recify the situation. My question is this, can a lot of driving in the mountains burn out the number 1 cylinder spark plug? I was recently on a trip in the Black Hills. The car ran fine until the day we departed. As we were leaving from Custer up hwy 385 the car suddenly began to misfire and the SES began flashing. It wasn't a bad misfire, but enough to throw the code. Being it was a Sunday and nothing would be open, we headed for home. Initially I thought it might have been bad gas from a small station we had filled up at the night before. After a couple of tanks of gas and a can of gas dryer, there has been no change. I got a code reading showing a P0301. I figured I would start with the plug wire and plug first. Is it possible it could be the power pack for that cylinder and how does one test it for a possible problem? The car had new plugs, wires, and 2 new power packs just about 2.5 years ago and new injectors back in the spring. Any thoughts would help?

[GTP Dad]

Usually the plug and wire are the place to start. Sometimes plugs on one cylinder will go bad before the others but it isn't common. If you have a great deal of detonation you can damage a plug in one cylinder and that could be the issue. The other issue may be due to the fuel injector going bad. Sometimes they develop high resistance and then will not put fuel to a certain cylinder. If you change the plug and wire and the misfire continues, change the fuel injectors around and see if the misfire changes. If it does then the injector is the issue. Finally, the coil usually will develop a double misfire as one coil fires two cylinders. However, anything is possible. So if the plug and wire change don't work and the injector is ok then the next step would be the coil. Although you might just want to change coils from one location to another to see if the misfire changes places just like with the injector.

[deb0704us]

My GP was rumbling and shaking this morning when I started it. The SES light went on. After a few miles it straightened itself out, but I dropped it off this evening anyway at the mechanic's to have a look. I'll let you know what they said.

[deb0704us]

Got new spark plugs, wires, fuel filter, and fuel injectors cleaned. Runs good now. Merry Christmas to me.

[GPFred]

Thanks GTP Dad. I did start with the spark wires. It turned out that the protective plastic wrap was resting up against the manifold. Needless to say, the wrapping and the wires were cooked. The #1 spark wire was cooked thru and cracked causing the arc, the #3 was not too far behind it. Changed out the wires and the car runs great again. I rerouted the wires away from the manifold and should have no more problems. Thanks for the info.