Running on 5 of 6 cylinders - running out of suggestions

[Huw Powell]

What is a "new used" coil?

Can you swap coils between cylinders?  If so, do so.

On 10/28/2012 5:49 PM, Andrew Muff wrote:
> 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.
>
>
>
>
>
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