Dead Cylinder

[georgeb]

My '92 auto developed a miss a few months ago and discovered one really low comp cyl and one about 50%. Since the two cylinders are next to each other a knowledgeable site member said it sounded like a head gasket burn-through between the cylinders. Since it wasn't my DD I decided to drive it locally and see if it got worse or the 2 bad cylinders equalized. I checked the comp yesterday and it is about the same after about a thousand miles. I'm thinking it's something else. Anyway to get a diagnosis without disassembly? I'm tempted to run it until something obvious surfaces.

[Dustin]

Get a leak-down tester. You'll need a compressor to do the test, but you'll be able to tell if you're leaking past the intake or exhaust valves, rings, or into the cooling system. Just have to take out the spark plugs.....

[kartracer46]

if I was to take a shot in the dark, my bet would be its just a burnt exhaust valve or two.

[Movin]

Is you gauge set the kind with a screw in hose? You can pop your disty cap
to see where the rotor is pointing. Go to that cylinder after you have pulled
all the spark plugs. Rotate the engine just enough to precisely locate that cylinder
at top dead center. If your adapter hose has a schrader check valve remove
it with a tire stem tool. Install the hose and plug it in to shop air. If you goofed
on TDC you will know
Take a piece of tubing or vacuum hose long enough to reach the spark plug
hole and your ear, listen carefully for a leak. You will want to listen in
adjoining spark plug holes for head gasket possibilities, open the throttle
body and listen for a burnt intake valve. Go to the tail pipe and listen for a
burnt exhaust valve. Listen at the dip stick tube or a nipple on the valve cover
for bad rings. Repeat this on all cylinders, making notes which one it is by rotor
position.

You will hear significant differences on the bad cylinder{s}
A bad head gasket can blow into an adjoining cylinder and
out the intake valve or exhaust valve but the noise will be
more apparent at the adjoining cylinders plug hole.

88 carbies may find they need a valve adjustment this way.

If you already have a cylinder leakdown tester you don't need
to read this!!!

[WmWatt]

On my car a leaking exhaust valve showed itself by carbon deposits on the underside of the valve cover, right over the leaky valve. In that case chemical cleaner dissolved the carbon buildup and fixed the problem. I've read that low compression on adjacent cylinders indicates a leaky head gasket.