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2001 STS P0300 Misfire


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So driving Saturday afternoon I noticed a slight hesitation/stumble @~60MPH, rolling to a stop light the SES began flashing and the stumble was obvious at idle. Limped it home ~8miles and the cat was stinking terribly bad in the driveway(cooking off unburnt fuel). Only code it was showing was PCM P0300 Misfire. Had a similar issue with the GF's old Grand Am a few years back - it ended up being a bad ICM after changing plugs, boots, and coil pack.

SO I puled the plugs yesterday and didn't notice any carbon tracking, all plugs were light brown/whitish except the left rear appeared wet. Hooked the plug to my push lawnmower and getting an orange spark - other plugs produce white spark(though smaller) and I was able to get a spark with the boot attached as well.

Anyone that's done them knows what a PITA the rear bank can be with the air valve back there so I'm going ahead with a new coil rail, and I figured since I haven't had a payment on this car in ~9yrs @124k mi changing all ignition components for $500 is a fair tradeoff.

The removed plugs were DENSO? were those OEM? I bought this car as a lease trade in(2-1/2yrs old @28k)

I'll update this thread if(fingers crossed) its back together and running properly this afternoon.

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That went well - running nice and smooth

I really debated reinstalling the third bolt on the air pump bracket but was able to get it stared and hand threaded in using the same piece of fuel hose I used to thread the plugs in.

It worked well for starting the rear coil pack bolts as well - the rear lower ones are pretty much blind and a tight turn if your fingers are big

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