strange engine problem, loss of power under load, strange noise Options

[mightyohm]

Hey all,

I'm having a strange engine problem that I'm hoping someone can help me diagnose.

When I give the car heavy throttle, I hear an intermittent noise that seems to be coming from the engine compartment. It's like a muffled banging or exhaust sound. When I hear the noise I feel a loss of power. When the car is warm, the sound is always accompanied by a whif of burning oil.

Aside from this problem the car is running fine - idle hasn't changed, no obvious misfiring. It's only under load that I have this problem.

It seems to happen the most when the engine is in its peak HP range - upwards of 3000 rpm.

This started happening about 6 months ago. I drive the car to work every day, so I have been noticing that it is slowly getting worse over time. Initially, it only happened when the car was cold, and completely went away after the car warmed up. Now it happens all the time, but it's still worst before the car has had a chance to warm up.

Any ideas? I'm fearing the worst - cyl to head leak? Cracked head??

[mightyohm]

r_towle - Not sure of the mileage or breakin, this motor was a hand-me-down from Mark. I've probably put 15k on it since I got it.

The good news - I replaced the spark plugs, cap and rotor and it seems to be running much better. The cap was particularly nasty. The weird sound I was hearing must have been a misfire under load. Very strange. Will see if it comes back.

The bad news - leakdown on #4 was two times higher than #3, so there is still something going on with that cylinder. Valves seem ok, and leakdown was to the crankcase, so it must be rings. Will keep driving it and see what happens. (IMG:style_emoticons/default/driving.gif)