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

[Lino Valadas]

If you have VAG-COM, run an output test (audible) and check the fuel injectors.  It may identify some issue with the first one, perhaps not the injector itself as you've already moved it around, but maybe the ECU, it may not be controlling it correctly.

Lino

Sent from my iPad

On 2012-10-28, at 6:14 PM, "Andrew Muff" <andrew at muffster.com> 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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