[V6-12v] Running on 5 of 6 cylinders - running out of suggestions

[Andrew Muff]

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.