Topic says it all... But let me give you a little more back-ground...

My engine doesn't have the power it should... it's got 154K miles on it... My friend 1991tealRSt-top ran a compression test on it when the engine was quite warm... he checked cylinders 4 and 6... #4 had 125PSI while #6 had 160...

Today I checked them all while relatively cold (ran engine for about 30-45 seconds before-hand) and they all held 160-170 PSI

Then I let the engine idle and heat up, took it for a few spirited drives around the block and came back. I checked cylinders 4 and 6. Both held right around 160-165 PSI...

If I pull the PVC valve, I get wisps of smoke, the same if I pull the dipstick out while cranking (never checked to see if it smoked while running)... I have no visible smoke from my tailpipes...

WHAT GIVES!!!

 

if your compression is good and the numbers are within 10% or so i wouldn't worry about it. doesn't sound like you're burning oil and you're bound to see "something" when you remove the pvc, comdensation burning off, steam from hot oil, blow by that isn't getting sucked back into the engine.

 

Why the variances in the tests the first time then?

Is it possible something is sticking? Or that something isn't sticking?

 

Did you perform all the tests the same way? The engine should be at operating temp. with all of the spark plugs removed and the engine should turn over 5 times for each hole you test.

Have you tried performing a leak-down test?


hth
nick

 

Don't forget to hold the throttle wide open while cranking for compression test.

 

I left all the plugs in and cranked until the compression didn't rise anymore. The throttle was closed. Why should all that matter? It took all the holes about the same time to raise the compression...

Perhaps later this afternoon I'll do it your way. It's going to be difficult to count out 5 RPM though...

 

If the throttle is closed, the cylinders won't fill with air... their fill path is blocked....

You remove all the plugs at the start of the procedure and leave them all out until you're finished so that the engine will spin at the same speed all the time no matter which cyl happens to have the gauge in it.

It's not real hard to count 5 compression strokes when all the plugs are out. When the engine comes around to the one that has the gauge in it, it will slow down.

Compression tests are meaningless exercises in grunt work if not doen properly.