Low compression on 2


Old 12-22-04, 06:19 AM
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Low compression on 2

I have a 3.0 Chrysler (Mitsibishi) v-6 engine. The compression on #2 cylander is far below specs while all other cylanders are normal for a vehicle with 100,000 miles. The car, at idol misses but at higher revs is fine with power to spare and good accelleration. The car does not appear to be smoking at any rpm.
How can I be definitive in my thinking that I should only lap in valves or do a full ring job?
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Old 12-22-04, 08:44 AM
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Did you also do a "wet" compression test? Squirt a few cc's of oil in the offending cylinder's plug hole, then recheck compression. If the compression goes up significantly, probably looking at rings. Otherwise maybe just a bad valve in that cylinder.
Old 12-22-04, 08:57 AM
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Yea, actually I did do that but forgot to mention it. The pressure rose about 10-12 psi in that cylander.
Old 12-22-04, 12:46 PM
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when doing a wet compression test the compression would come up significatly if it was a ring problem if it only came up 10 psi I would suspect a valve problem.
Old 12-22-04, 10:22 PM
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Thanks guys. That's what we figured as well. Just wanting to double check. Never used this web site before but have heard about it from friends. Good site, good info.
Old 12-23-04, 02:28 PM
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FYI: The older Mopar 3.0's are known for valves Guides dropping down, thus not letting the valve fully seat they changed the design in later years. Not sure what year, You may want to check the guides.

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