Random low compression?

[Ether-D]

1992 m20b25.

This motor usually starts right up and purrs like a kitten, but twice, I've gone to start it and it turns over really fast like it has no compression. It doesn't have it's normal "rhythm" (regadega-regadega-vroom) when starting. It also takes about 30 seconds of cranking before it finally half asses it's way to life, missing, only half starting at first. Then, runs perfect. Strong. Good 'n' strong. Doesn't miss a lick until the next time it does it, maybe 3 months later.

It's only happened twice since I put the yard motor in my car about 6 months ago. Fresh head, new head gasket (goetze), new head bolts. All new seals and gaskets.

It does seem to have an oil leak really high up on the front of the motor. I can't tell from where.

Any ideas?

[SmokeE30]

Have you done a leak down test on it, if its actually loosing compression in some cylinders only thing I an think that would make it intermittent is sticking valves, if a valve or two is hanging open due to pervious contact with a piston or similar. Run a leak down test to confirm if it actually has good compression on all cylinders

[Ether-D]

It has 150 on all but #2 and it has 135. I've had a sticky valve before on a different head. I'm 99% sure it's not a sticky valve. I feel like it has something to do with the HG, but I've never heard of such randomness.

Edit: And there's been no pervious contact with that engine. I'm on the nofap challenge.;D

[jlevie]

A bad head gasket won't cause a random compression loss. The only thing that can cause that is sticking valves. All other causes of loss of compression are constant.

[E30NJ]

You could squirt some oil in cylinder #2 to see if the compression raises which means worn piston rings. Other than that, what about the fuel pump?