I just did my first compression test. I removed all 4 spark plugs, pulled fuse 15a, but while cranking the engine over I forgot to push the gas pedal to the floor. Are these results still accurate, and what exactly does having the throttle wide open do?

Here are my results. I have a 99 Civic Si. There are 2 sets of numbers, one set I cranked the engine over 12 times, the other 5:


12 times: C1=215, C2=215, C3=220, C4=220

5 times: C1=205-210(inbetween), C2=205-210(inbetween), C3=210, C4=210

I'm concerned that in both sets of results, cylinder 1 and 2 are both lower than 3 and 4. What does this mean? Also, some people keep cranking until the needle stops, but others crank a certain amount, like 5. Which results, if any (since the throttle wasn't wide open) are accurate? Thanks for helping the mechanically challenged!

 

The difference really isnt that big to worry.

 

Thanks man, but do you know what difference it makes if the throttle is wide open? Will my readings be lower? I've read a lot of posts telling people to do this, but have never found an explanation why. I just completely forgot!

 

Why would it even matter? The engine isnt running...there is no spark!

 

LOL, I have no idea! That's why I'm asking the question. On C-SPEED, as well as other threads on H-T, most people say to make sure the throttle is wide open. Here is a link to what I'm talking about:

http://www.c-speedracing.com/howto/c...t/comptest.php

"Have someone hold the compression tester while you press the gas pedal all the way to the floor, this is very important. While the pedal is pressed down, turn the ignition on and crank the motor over 5 times."

He says "this is very important"--WHY????

 

I think what is important is if the needle jumps fast to say 200 (as an example) on the first crank, then will creep a little after each crank. If the needle goes slow to 200 on the first crank, then something's not good. Correct me if I'm wrong...


[Modified by Chrome Pipes, 10:59 PM 1/23/2003]

 

I wouldn't sweat it. Your numbers look real good. You are allowed up to 25 to 30 psi between cylinders.