Compression issues

[Mikecraig80]

I have a 94 XLT and just did cylinder compression checks as follows #1-135, #2 -145, #3- 160, #4-150, #5-180, #6-190 . Where do I proceed from there? Engine has 265,000 on it and ran great till it started running like crap off and on then died.

 

[natenkiki2004]

Those do vary quite a bit but I'd argue that considering the miles, they're not going to be a source of sudden performance issues. Now, if one was around 40 PSI, sure, you might have bent an intake pushrod or burned a valve. Look elsewhere for performance issues. Plugs, wires, vacuum leaks, KOEO/KOER test.

 

[Mikecraig80]

Those do vary quite a bit but I'd argue that considering the miles, they're not going to be a source of sudden performance issues. Now, if one was around 40 PSI, sure, you might have bent an intake pushrod or burned a valve. Look elsewhere for performance issues. Plugs, wires, vacuum leaks, KOEO/KOER test.

During the first round of compression checks, #3 cylinder read 90 lbs. After checking all of them I went back to verify #3 and it read 160. So it doesn't seem apparent the trouble has to do with the head, head gasket or block.

 

[natenkiki2004]

You bring up a point I failed to mention as my mind drifted off. Compression numbers can change depending on testing methods. I did a test on an Oldsmobile and the more I went, the lower the numbers got. The battery was draining I would test them forwards and backwards, charging the battery in-between (maybe wait a day between). Jump the starter solenoid, no key in the ignition (no fuel dumping into cylinders).

But again, like you said, I'd doubt it's an issue caused by heads or compression at this point.

 

[Mikecraig80]

You bring up a point I failed to mention as my mind drifted off. Compression numbers can change depending on testing methods. I did a test on an Oldsmobile and the more I went, the lower the numbers got. The battery was draining I would test them forwards and backwards, charging the battery in-between (maybe wait a day between). Jump the starter solenoid, no key in the ignition (no fuel dumping into cylinders).

But again, like you said, I'd doubt it's an issue caused by heads or compression at this point.

 

[Mikecraig80]

Thanks