Which cylinder is which?

[06scoobyrex]

Yeah... you might be able to see if there is anything wrong, but usally you'll have to remove the head itself to see if the valve or valve seat is burned or warped... A leakdown test will be able to tell you where your loosing compression from and its a lot less of a hastle...

[noballoffire]

Alright, I'm taking it in Wednesday, and I'll have them do a leakdown test first. Go from there.

Possibly (un)Related question: I've been driving for a few weeks like this (CEL blinkage and all), and out of the blue my radiator cracked last Thursday. Huge crack, right on top. Could that be related?

[06scoobyrex]

That sounds like a headgasket issue that might be causing low compression... if that's the case then that's good news, cause that's a hell of a lot cheaper fix then a rebuild... I wasn't so lucky, I had cylinder wall and piston damage... $5K later my car runs great and have my timing belt service, clutch job, and new engine out of the way...lol the leakdown test should tell you exactly what's going on and when your CEL is blinking and goes away it means there is unburned fuel hitting the catalyic converter or if it continues to blink then its a major misfire... If you can try not to drive the car as much as possible to pervent the chance of causing anymore damage...