engine misses at idle speed

PONTIAC GRAND AM
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MONFILSD
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  • 2 POSTS
I have a 2001 pontiac grand am with a 2.4l engine the mileage is 99000 km. My engine misses at idle speed, it will idle at 600 rpm and then it will drop at 400 rpm for a split second. i can hear from the muffler a backfire of air. I had it checked with a computer and it says that the 4th cylinder has a random misfire. I have changed the plugs, boots, fuel filter and checked the coils they still have a 6.4 ohm rating. What can be the cause?
Please Help!

I found the problem.... Never use "bosh" spark plugs. They do not have the proper heat range so they do not provide a proper spark causing a misfire code in the pcm.[img:c4b031b5c3]http://www.2carpros.com/forum/automotive_pictures/90091_Cars_RPM64_L_1.jpg[/img:c4b031b5c3]
Aug 1, 2007 at 11:22 PM
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MONFILSD
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DO NOT BUY BOSH SPARK PLUGS FOR GM VEHICLES.
This was my problem. they do not output enough HEAT to burn fuel properly. so use DELCO OR NGK plugs and your car will work fine.
Mar 28, 2008 at 9:33 AM
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MASTERTECHTIM
  • ✓Experienced Mechanic
  • 4,750 POSTS
has it been skipping since august? did the skip start right after you put in the bosch plugs? are you sure it wasnt cracked? im curious why it skipped. i never liked bosch plugs, i always use ac delco if possible.
Mar 28, 2008 at 10:24 AM
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