My 99 Trans am died on me the other day. I was driving about 80 and had a sudden loss of power and the SES light started flashing. So I pulled over and the engine was running very rough at about 500 RPM. There was a bad knock from coming from around cylinder #7. We plugged in a scanner, it got no signal from the computer. That led us to think it was a computer problem. Turned out the computer was fine. A compression test showed #7 has zero compression. The rest tested fine. There is no gas in the oil and no smoke coming from the exhaust. What the hell could be wrong? Any suggestions?

 

You burned a hole through a piston, broke a valve, or blew a hole through the side of the bore. My vote is for broken valve. Hopefully. Good luck! Use it as an excuse for some bad heads and a cam....

 

2 votes for a broken valve

 

Valve or rocker arm are my votes.

(maybe baddly bent pushrod....)


Gordon

 

hmm I would love to know what that is...

I will go with rocker or spring.. which would indirectly be valve.. hehe

 

Bent valve.................seriously. It happened a little over a year ago to my dad's truck, and the compression in cylinder 4 was ZERO --- not "a couple pounds" --- zero. As well, a friend was fixing an intake gasket leak on a 3.1L V6, and by mistake installed the wrong push rods back into their homes (swapped intake for exhaust) on one of the cylinders, and when he started the engine, it was "ticking" really bad. Well, after doing a compression test, he found zero compression in one of the cylinders, and sure enough, after pulling the head back off, found a bent valve and a piston with a valve mark in it.

Is your car a standard?? Not to say you can't over-rev an auto, but it's more likely with a stick that the engine over-revved a little causing the valves to float and the piston hit a valve. Sorry to say, but your motor's gotta come apart.

 

You might have a burned valve.. There is a way you can tell if it is a burnt valve is by taking out the plugs and do another compression test, then try squirting oil in to #7 Cylinder and if it does have compression it is more likely a burnt valve... You have to check and then pull off valve cover and if it is a broken vavle spring, you can get a tool to replace valve spring w/ out having to pull the heads..

I would try the oil trick first.. Though..

 

I don't know that the oil trick works with valves. That is for worn rings (temporarily fills in the gap). Even with broken rings, you would still get some compression.

Pull a valve cover. I don't think you are going to see much.....maybe if it is a broken spring. I think you broke/burnt a valve, and you won't know unless the head comes off. Not really THAT hard on these cars. Get some bad CNC'd heads and a cam....or just get the valve replaced and consider yourself lucky.....Let us know!