1G Compression Test Results

[604CruisinCroat]

A buddy of mine did a quick dry compression test on my car. The engine was a little cold and throttle was not at WOT, I burn NO oil, my oil is always clean, and my valve cover gasket leaks. Compression is as follows:

150
130
130
150

I'm a little worried, and assume it's bad valve seals. Once again, I have not a hint of smoke out of my exhaust, except in the mornings when it's cold out (white), that's about it.

Any comments/suggestions? Thanks.

 

[4g63tsiawd]

Do a leak down test, your comprsion look decent for being cold.

 

[Snail Tuning]

those numbers are almost exactly like mine. I have 144k miles on my engine, and my numbers were identical. 150 on both ends, and about 130-130 in middle 2.

so you should be right on.

 

[Xero_Tolerance]

Isn't compression supposed to be 163 or so for all cylinders?

 

[4g63tsiawd]

Factory spec is 165psi out of the plant. Service on the rings is 121psi, seeing that he did it with cold engine it should be a little higher.

 

[johnk]

Might be a HG two adjacent cylinders are low.

 

[bigemrich]

At any rate, there is a problem with the middle cylinders because they are more than 14 psi lower than the others. Could be a headgasket because of the adjacent cylinders, or trouble with the valves or head. I would say something is wrong somewhere.

--Kyle

 

[oldman]

Do the compression again and make sure it's done correctly, operating temperature and WOT. I think you're fine, valve seals are not part of the compression test.

 

[DSMRevolution]

Are you sure WOT disables fuel on our DSMs? On mine I don't believe it does. Better yet, pull the fuel pump fuse and disconnect the coil connector on the back of the coil (disables spark). Anyways I agree, do another test with the engine at operating temp. Also if you can get your hands on a leakdown tester that will tell you wether it is your headgasket or not.

 

[oldman]

Are you sure WOT disables fuel on our DSMs? On mine I don't believe it does. Better yet, pull the fuel pump fuse and disconnect the coil connector on the back of the coil (disables spark). Anyways I agree, do another test with the engine at operating temp. Also if you can get your hands on a leakdown tester that will tell you wether it is your headgasket or not.

WOT during the compression test, not for dissabling the fuel. The MPI fuse and coil part I thought he knew already since he's done the test before.

 

[DSMRevolution]

WOT during the compression test, not for dissabling the fuel. The MPI fuse and coil part I thought he knew already since he's done the test before.

Yeah I would assume too but you might be surprised. I am not doubting him, just confirming everything What is the purpose of WOT during the compression test? All that is going to do is open the throttle body and set the TPS at 100% throttle position. I don't think the ECU disables the fuel when it sees 100% throttle position with the engine off like some vehicles. You are measuring cylinder pressure which has nothing to do with the intake track.

I am not saying anybody is wrong or giving anybody a hard time, just trying to understand where everybody is coming from.

 

[oldman]

Yeah I would assume too but you might be surprised. I am not doubting him, just confirming everything What is the purpose of WOT during the compression test? All that is going to do is open the throttle body and set the TPS at 100% throttle position. I don't think the ECU disables the fuel when it sees 100% throttle position with the engine off like some vehicles. You are measuring cylinder pressure which has nothing to do with the intake track.

I am not saying anybody is wrong or giving anybody a hard time, just trying to understand where everybody is coming from.

http://www.geocities.com/dsmgrrrl/FAQs/compression.htm

Only going by the procedure decribed here. why? My guess would be to provide free flow of air to the head without generating vacumm in the intake manifold during cranking. Now that's return the thread to it's owner.