A friend of mine had his SES light come on so I autotapped. It looks like a P0300 DTC was set at idle. I have done a search and found some info to help me. Use the search, it works!

However, when we did some WOT runs, I noticed that the msfires rack up on ALL cylinders at high RPMS (above 4500). I'm not sure this is related to the P0300 becuase the P0300 code was set at idle. I thought it may be the plugs because he had stock plugs gapped at .060. We changed plugs to TR55IX gapped at .055 (3.4" pulley) but it didn't help. Also, the wires were recently replaced (stock Packards).

What else could cause high RPM misfires? Could the coils be bad? I recall a TSB on the '97 that a PCM reflash was necessary to remedy this. Am I on crack?

All help is appreciated!

-Alex

I have had the same problem. The dealer I took my '98 GTP to showed the same P0300 error. They said it could be the 3.4 pully due to the added air. I think they were just guessing. I don't know what the fix for it could be but let me know if you find out. Have you ran the car with the 3.8 pully on? Does it run fine like that?

My car, as well as thousands of others, is running a 3.4" pulley without problems. I believe your problem, as well as my friend's, is in the ignition system. I don't think my friend's P0300 has anything to do with the high rpm misfires. If the P0300 is your only problem, have a look at this:

http://members.cox.net/franklin147/images/DTC/P0300.html

There are quite a few things that can cause a P0300.

HTH,
-Alex

After I swapped to a 3.4 pulley my car set a P0300 code and had what I thought was a high rpm miss. Turned out that the belt was slipping at upper rpm. A Gatorback fixed it.