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Just ran compression, have quest.

667 Views 6 Replies 1 Participant Last post by  New Owner
I just ran a compression check last night on my car and here is what I came up with.
cyl 1 - 182
cyl 2 - 186
cyl 3 - 185
cyl 4 - 185
cyl 5 - 185
cyl 6 - 177

These numbers seem a little high to me after comparing them against what others have seen. I did the test by removing all the sparkplugs and then turning over the engine until the guage stopped climbing. Also the engine was warmed up at the time I did the test. Is this the correct way to do it?


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I assumed you disconnected the proper things as it says to do in the manual. I ran my test with the accelerator to the floor as well. If you don't you will get lower numbers. (At least I did). Everyone says, though, that the conditions and gauge can vary. So basically unless you are at, say, 100 or less or there is a big difference between on cylinder to the next, you should be OK. I haven't been able to get anyone to answer what is the maximum variation from max cylinder to min cylinder pressure, yet, though.


I didn't know to disconnect other things besides removing the sparkplugs. I'm coming over from the mustang crowd so all I know is N/A V8's.
Basically all I did was pull out all the sparkplugs and turn the engine over until the guage stopped moving.
I don't like holding the throttle down when doing the test because I beleive you're putting a lot of fuel into the combustion chamber by doing that.
You shouldn't have more than a 15psi diff between cylinders.
Pull EFI fuses 1&2, then keep the throttle plate open. Was there gas on the compression tester? If you kept those fuses in there should have been.
I smelled a little gas, but not too much. Probably evaporated rather quickly or went into the oil pan.
Good numbers, kinda too high for a dry compression check tho. You should change your oil, since gas might've contamiated it.

You need to disconnect CAS (Crank Angle Sensor(s)), and pull both EFI fuses next time you do it.
Thanks for the help. When I did the compression test the car had been at it's operating temperature. I only let it sit for about an hour before I started in on it. I've always done the test this way on previous cars though.
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