Pontiac Repair: 01 Montana 3.4L Misfire, chevron techron, ac delco

Question
I have an 01 Montana the is misfiring on cylinder #5. The check engine light came on and stayed on. I filled up with premium gas and added a can of injector cleaner (seafoam). A couple miles down the highway the light went off and the van was running fine. The next day it started to misfire again when getting up to highway speeds and at idle. When parked I can rev the engine to 4000 rpm and it will consistently misfire as the gauge reaches 4k. Plugs and wires or do you think something else?

Thanks, Bob

Answer
Hi Bob:

More then likely it's a plug wire issue. With the van bing 9 years old now it more then likley has the original set still on it or if they were replaced maybe a cheap set was put on it. Buy a good set from NAPA or Carquest or even better a set of AC delco wires. If the van has close to 100,000 miles on it replace the plugs as well ONLY USE AC delco nothing else. Do not waaste your $ on premium fuel use only 87 octane and you may also want to replace the fuel filter that is overlooked ALL the time you can use an after market filter Wix is a good name barnd to buy or Fram. Lastly if you want to use an injector cleaner only use Chevron Techron cleaner that works the best and Gm sells it at the dealer with a Goodwrench lable but it's Chevron Techron. If it is still misfiring after that then your going to have to look further into the problem. If you do replace the wires take not of the metal contacts on the tops of the coils wher the wires attach if any of them are black and burnt or rusted replace that coil as well. Good luck :)