Confused..My compression test does not add up!

[teklord69]

I searched this forum, google, etc..Seems like my compression test should be in the 180's to 200 range. I got 120 psi +/- 2 lbs psi on all 4 cylinders. Some say this is even too low for combustion to happen. I didnt do a "wet" test.

Here is the thing..The car runs smooth, pulls failry hard..car does not burn oil, no white smoke coming out. I just recently changed the profile gasket as well as the head gasket.

How are people getting 200 psi?  I understand if my car runs like crap but it doesn't. Here are my steps in doing the compression test:

1. Rented compression tester from Autozone.
2. Ran car to operating temp.
3. Removed all spark plugs.
4. Removed fuse for fuel pump.
5. Got in car and floored throttle.
6. Turned the engine up to 8 times.

What am I doing wrong here? Are people gettng 200+ have all plugs out?

[DesktopDave]

Sounds like you did everything right.  Consistency is the key.  If all your readings are low & the car runs great, assume it's OK.  Shouldn't matter if the plugs are out, but that's how I do mine for convenience's sake.

FWIW, I'd block the intake all the way open & repeat the test.  Also be sure you don't have a vac damper that's jammed or plugged on the comp tester.  That'd make it read low too.

[teklord69]

Sounds like you did everything right.  Consistency is the key.  If all your readings are low & the car runs great, assume it's OK.  Shouldn't matter if the plugs are out, but that's how I do mine for convenience's sake.

FWIW, I'd block the intake all the way open & repeat the test.  Also be sure you don't have a vac damper that's jammed or plugged on the comp tester.  That'd make it read low too.

Ok, I was able to acquire the Bentley manual..The acceptable range is from 150-180 I believe.. So I am not that far off ( not sure how some people get 220 lbs +)..

I did the steps on what Bentley recommends for compression test but one thing I didnt do is remove the Fuel pump relay and the DME relay..(all I did was remove the fuel pump fuse). I am not sure if that would matter and change the result of my test?

[Ryann]

My guess would be that the comp. guage you rented is a p.o.s. .

[VegasKyle]

Like others have said pay less attention to the actual numbers and more attention to the spread between them.  If you are worried get a known good gauge and try again.

[rjcaptsean]

I ran a check on mine and came out with 230 for 1,2, and 3 and then 210 for 4.  I will look at my gauge when I get home to see if perhaps it calibrated in different increments and I just took it for granted it was psi.