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Old 03-16-2012, 10:33 PM   #11 (permalink)
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Default drive by wire, fuel injection, cold engines

Quote: Originally Posted by Zenkat View Post
I've read warm engine, but not hot. Gas pedal to the floor when cranking, all plugs removed, etc. Gas pedal didn't seem to make much difference the last time i checked mine, but it usually raises the pressure up a tad.

Gas pedal position on fuel injected and throttle position sensor (wireless) cars won't change the compression reading. The compression reading is for how tight the piston rings & valve & seals etc are holding.
Listening to the start up of a COLD engine will give instant clues to mechanical engine problems. Knocking, suspicious valve rattle, clunking or any exhaust smoking or misfiring or long starter activity.
Compression tests are usually done on warm, but not HOT engines. Since engines will typically wear evenly, looking for an odd LOW reading from one cylinder will possibly indicate mechanical problems.
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