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Amp67 05-26-2009 09:54 PM

compression testing results
Hello all, this past weekend I borrowed a compression testing tool from my friend. I tested on a stone cold engine (sat for 48 hours). I cranked for 3 seconds on each cylinder (about 10 revs). Here is what I got from left to right (passenger to driver side):
178, 195, 190, 176

Any comments? I know that you hope for consistency in readings, these are reasonably close, considering a sample size of 1 per cylinder.

I had no real reason to test compression, mostly curiosity. I wanted to know if I had a really bad cylinder. My idle quality isn't bad, not terribly good either. My mounts were all changed. I will look for an intake leak next.

One interesting observation is the plugs. They all were slightly sooted up around the base. I changed these plugs about 15K miles ago. The replaced plugs were clean. What did happen since the plugs were changed was a coolant flush and a Tstat change. The previous Tstat had the engine running colder (5/16). Now the engine runs at 7/16 on the coolant temp gauge. I am thinking the cooler running engine caused the sooting up of the plugs. On the other hand my original O2 sensor could be going south and having the engine run slightly richer. My fuel economy has not suffered though.

As always, I am very thankful for all the knowledge this site delivers, great!:yes:

mr18436572 05-27-2009 01:46 PM

Re: compression testing results
Those readings dont really indicate a dead cylinder.

madpogue 05-27-2009 01:49 PM

Re: compression testing results
Only two are below the 180-psi service limit, and by just a few psi, and that's probably attributable to it being done on a cold engine. I'd bet a nickel they'd all be well above the minimum when tested hot.

OldNuc 05-27-2009 01:54 PM

Re: compression testing results
Crank the engine till the gauge quits increasing when the engine is cold.

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