My 91' TSi is acting like it has a miss, but can't figure out why. split headgasket?

[Boehlldozer]

My car gradually developed a "misfire" so to speak over the past few months. Along with this, the exhaust also smells really, really rich (it burns my nose and eyes and makes the drivers behind me complain, etc...) There is also a huffing and puffing noise that can be heard echoing inside of the exhaust system when I stand behind the car, and if I put a piece of paper over the end of the tailpipes, it flaps against the pipe's opening quite violently, as if the back pressure reverses itself during these "huffs".

Here are the things that I checked and replaced in an attempt to remedy this, at first, seemingly simple issue:

Installed:
New spark plugs (I thought the old ones looked okay though)
New spark plug wires
New PCV valve
New fuel filter
New EGR gasket

Checked:
Ignition coil resistance values, they turned out good.
Fuel injector resistance values, no problems.
Used the stethoscope method (a screwdriver) to check the operation of the fuel injectors, all seemed functioning (ticking) consistently.
I bought an ignition timing light (inductive type) and found the timing was spot on.
MAF resistance values, also good.
O2 sensor resistance, good as well.
EGR valve, seemed to function properly
Cylinder compression was a bit weird though. (explained below)

When I checked the cylinder compression, it was good in two of the cylinders, but the two others on the timing belt side were a bit lower, but still technically within specs. My exhaust looks good in the sense that there is no white or blue smoke, and the car doesn't use much, if any oil between changes. I am aware though that between the cylinders in this engine, there are no oil or coolant passages. My big question here is, could something like a cracked head gasket between two cylinders cause a misfire, or misfire-like symptoms? and if this is not the case, what else could be the cause?

Any help or ideas you have are much appreciated, Thanks!!!!!

[Papa George]

what are the cylinder compression you could have a stuck exhaust valve or one that is not closing all the way. also could have a bad ring.

a leak down test is the best way to check for a bad valve or ring.

during the test you can remove the oil filler cap and look for air coming out, if the rings are bad it will leak. if a valve was bad you will feel it from the exhaust pipe.

[Boehlldozer]

THANKS!!! That sounds like a good idea, I have an air compressor, but how do I get the air into the cylinder? (I've only heard about leak down tests, but never done one) Is there a fitting I can buy that hooks up to the air hose and screws into the spark plug well?

[Papa George]

Yes you can get the adapter kit from you local auto store or if you have a Harbor freight they sell them, you screw it in to the plug hole set the pressure on your compressor to no more then what your manual says your cylinder compressor should be.

Oh yes make sure the cylinder is at top dead center

Good Luck

[Boehlldozer]

Okay, so I replaced the ignition coil because it had a broken post that was fixed in a not so sturdy way, but it still acts pretty much the same. Now though, there is a lot of ticking coming from the motor that sounds like electricity arching from the plug wires (the brand new plug wires), but there is no spark visible from them. I also listened to the injectors again to see if they were the culprit, they still seemed fine. Is there anything that could be causing this noise that could have to do with the engine running so rough?

I posted a video of it on youtube:

http://www.youtube.com/watch?v=rKxPZ1wL_O0

[ned032002]

Sounds to me like a bad injector(s). I'm not sure so don't go replacing them yet but it thats what it seems like to me.

[Boehlldozer]

Okay, so I found out that the intake manifold gasket was completely blown out of the top of the #1 cylinder intake runner. I attribute that to the fact that the two top bolts were missing out of the intake manifold support bracket. When replacing the gasket, I noticed that the knock sensor had completely melted, and I mean completely. It's very sticky, tree sap-like remains were strewn down the back of my engine block like a waterfall of hardened molasses. So after peeling off the unwanted sandy residue and installing a new knock sensor and replacing the intake manifold gasket (I thoroughly cleaned the inside of the manifold too to get rid of all the mucky buildup too of course) the engine now runs perfectly. I can hardly tell its on when its idling

Though, I'm still curious..what the hell caused my knock sensor to melt!?!?

[SilvrEclipse]

Boost leaks and the most common problem when these cars have a miss or run bad. Glad you got it fixed.