changed plugs and checked compression. 1-155, 2-125, 3-145, 4-145, 5-145. is this enough diff to cause the misfire and would it be the cyl head problem the tsb is about?
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2005 Chevrolet Colorado
Question: PO302 code
Answer #1patrick mannion from Greg Solow's Engine Room, January 11, 2010, 21:32Master
I would drive the truck and recheck the compression, sometimes after "loosening the spark plugs carbon gets dislodged and gives a false low compression reading. Also your reading look low all round, try to check the compression with the throttle fully opened, it will allow more air past the throttle butterfly and give better readings with more proper cylinder filling.
Service bulletin 07123 refers to valve seat wear and may be your problem there is an extended campaign regarding this "known problem".
04 06 04081C Service Bulletin issued August 18, 2005 is interesting, it address specifically misfire codes due to valve spring problems! Call Chevy they should have extended warentee to cover this.
Replyjfbj664, January 14, 2010, 12:53Rookie
we have 139000 miles. warranty only to 100000. would like to know what they would have done to see if this is the problem and if so what they would have done?
Replypatrick mannion, January 14, 2010, 13:05Master
I suppose you need a firm diagnoses of what is actually causing the low cylinder compression/misfire in that cylinder. A cylinder leakage test will determine if your engine has "leakage "past the rings/cylinder, or valves/ Once this is determined I would see if the problem is related or pertinent to the Service Bulletin and then call Chevy North America customer service sometimes they offer "a good will gesture" for known problems.