Voyager2

1: 140
2: 140
3: 150
4: 165
5: 153
6: 143

Is it strange that cyl 4 is that high?

These are dry numbers done on a warm engine.

joeyv44

Seems alright to me, Compression should read 120 to 150 psi, with no more than a 30 variance. What made you do a compression test to begin with?

cruiser54

You're fine.

andrewmp6

Its a mass production engine is why the numbers very that much,But everything is with in close enough spec to me not to worry about anything.

Voyager2

I'm trying to diagnose a P0301, and this was one of my steps along the way.

I figured I was in the clear with #1, but I didn't know if #4 could be some other problem, being so much higher than the others.

I appreciate the feedback folks.

Not too bad for an engine with almost 220,000 miles?

cruiser54

P0301 can be caused by weak valve springs on that cylinder.

Also, a dirty injector, among other things including carbon under the exhaust valve from the weak valve springs.

.

Voyager2

How can I test for weak valve springs?

cruiser54

You just put new ones in.

But, before you go through all that, try this: