Danno

I've had cracked rings on all four cylinders once. One of them was so bad, it worked its way up into the combustion chamber and dented up the cylinder-head and piston pretty bad. Another piston had a triangular hole melted into its edge about 3/4" long....

Yan

Ok guys, here's a better summary:

1) I got fuel
2) I got sparks
3) Cylinder #1 = 140, #2 = 140, #3 = 0, #4 = 125

There's no weird noise, everything is turning fine, no smoke, the spark plugs don't show any bad sign.

What's the easiest way to diagnose a bad valve or holed piston? Can we check the piston with a small light thru the hole of the spark plug?

I know that I'll have to open it anyway, I just want to start shopping for the necessary parts. What are the next steps and how much am I looking to spend for each of the possible culprits?

Jfrahm

Wow, bad news.

Can you borrow a borescope? Or bring it up to TDC on the compression stroke, put compressed air into the cyl (not too much) and see where it comes back out (intake, exhaust, or breather?)

-Joel.

Yan

No I don't have access to that kind of equipment, I hoped that there was a better way to identify the culprit.

Tom M'Guinn

Sorry about that. If you pump compressed air into the cylinder when the valves are shut (or supposed to be), you should be able to get a clue based on where the air comes out -- out the intake is bad intake valve, out the exhaust is bad exhaust valve, out the crankcase is bad rings or holed piston or cracked cylinder.

krutschman1

P U L L T H E H E A D ! Stop posting, and start wrenching. You could've been done already!

hosrom_951

I know a friend of mine who was pushing his boxster really hard, redlining on 3rd gear, then shifts to 2nd by mistake, and boom goes the engine. 5 out of the 6 cylinders were working. Compression showed that that cylinder was 0. Pulled out the engine, and found disaster. Needed and NEW engine or a used one...........

turbo951fan

Yes, no matter what, pull it and you know. Probably a valve, they just go once in a while. No biggie.