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Old 10-19-2018, 01:57 PM   #41
Cape Codder
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Join Date: May 2010
Posts: 985
Default Re: Terriable backfiring

Sooo....I have checked a couple things that were suggested. Started the engine and ran for several minutes to warm it up. Grounded each plug and each showed a difference in idle. Don't understand BUT I will be putting in NEW Champion W18 plugs. I think they are a colder running plug but....... I then took the car around town for perhaps 10 miles and it backfired a couple of times, and several times actually quite. At the end of driving the engine was really smooth. I also removed the plugs and did a compression check. 1 - 2 - 4 shoed 60 pounds BUT 3 showed at best 48 pounds. Do I have a head gasket problem? Always thought that a 10% variance in pressure was acceptable but this is 20%.
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