Muffster1

Hey guys,

I have a 1995 Audi A6 Quattro with the 2.8L SOHC engine (AFC) which I’ve just gone through and rebuilt the cylinder heads after a blown head gasket. I should mention that I bought the car with the blown head gasket so I don’t know what it ran like before I bought it.

When I started it up for the first time, 2 cylinders did not fire. It blew a fair amount of white smoke from the exhaust and ran rough. I solved one of them by finding a loose ignition coil wire. Now it puts out white smoke only under a heavy load (full throttle) and runs reasonably smooth but not perfect. When I inspect the spark plugs, #1 cylinder is black and sooty while all the rest are clean and look fine. So here’s what I’ve done to rule things out:

• I’ve swapped the spark plugs for #1 and #4 cylinders. Each time I clean the sooty one and put it in #4. After I run it a bit, #4 plug is now clean and #1 is sooty again. – So not a plug issue.
• I’ve tested the resistance of the wire and found it to be in spec. I’ve also swapped the #1 wire with the other short one (#6 I think). Same issue with #1. – So not a wire issue.
• I’ve tested the spark by holding the spark plug with insulated pliers and rubber gloves next to the engine block. After shocking the crap out of me once, I tried it again standing on a rubber pad. I see spark, but wasn’t convinced it was a strong spark so I replaced the ignition coil with a new used one. Still fouling up #1. – so not the ignition coil.
• I’ve swapped the #1 fuel injector with the one from #2. I’ve also tested the voltage from the #1 injector wire and I get a signal. – So not the fuel injector.
• I’ve tested the compression for #1 (and all of them). Good compression. (BTW – I had the heads vacuum tested with the valves in and they came back good. Also, during the head rebuild I removed the valves and lapped them and also replaced all valve stem seals). I took the valve cover off and rotated the engine by hand watching the cam press the valves open and closed. No issues there. – So not the rings or valves.

I’m at a loss as what to test next. I keep going back to the old trifecta of engines – it’s either fuel, air, or spark. I know for sure it’s getting spark and it’s timed right. I know there is fuel because it puts out white smoke and the plug gets fouled with carbon deposits. I know it’s getting air because I’ve inspected the intake manifold when I had it off and there is nothing wrong with it – plus I have a hard time believing that 5 of 6 cylinders are getting air but not #1.

I’d love to hear what anybody thinks about this. What should I test next? Am I missing something and should retest one of the things I’ve already listed?

Oh, one more thing. The VAG-COM reports no codes for a misfire but does say the EGR is failing. I suspect that’s just because the white smoke is overloading the EGR. Once I get the cylinder to fire I’m thinking that will go away.

grillage

I had a 12v that fouled my #4 plug similarly. Is it oily fouling?

If that's the case, I tracked mine down to a broken oil control ring in that cylinder. Oil was coming past it and into the cylinder causing the plug to foul and not fire

Muffster1

It's not oily, but rather carbon fouled. I have an idea of what it is, but don't want to spoil the punch line until I've pulled a few things off this weekend to confirm. After that I'll post what is the final outcome.