audijim113

99 A6 2.8 30 V non turbo Started missing yesterday and CEL came on. Humidity is a little high, but it wasn't raining when I first noticed it or the light came on. Misses most when cold or accelerating.

Code = Missfire # 3

Swapped plugs, still misses, still code for #3
Swapped wires, still misses, still code for #3

Mechanic thinks it is the injector. I'm running a bottle of techron through it, but he thinks it is the electrical part not dirty inj.

How common is injector failure?

Is it possible that just one part of the coil is bad?

Any other possible causes?

4Driver4

check the spark plug?

Rocky-in-Connecticut

fouled injector? This would not throw a code but bad fuel spray could be your problem. If you are able to swap injectors but I'd run some techron first.

dave240Z

I had the same problem on our old Passat 4Motion. Problem easily diagnosed by scanning with VAG, then moving injector to another cylinder and re-scanning. Problem followed. Turned out to be a leaky injector. New injectors aren't terribly expensive (~$30?) and it took me less than 30min to replace from start to finish. VAG-COM more than paid for itself right there.

Swapping injectors is not terribly difficult. However, this won't do you any good unless you have a VAG handy.

MP4.2+6.0

swap the coil unit from one plug to another too, not just the wire.

audijim113

If it had coil on plug, there wouldn't have been any wires to swap.

Next, I did swap the plugs as it said in my post

Bottle of techron in there from yesterday. Slim chance, but for $5 bucks it's worth a try. Mechanic changing injector tomorrow. I looked at it and the rail and all 3 injectors have to come up to get the center one. Also all the seals will be replaced. He estimates 3 hrs, which seems right to me. I could do it myself, but just don't have the time.

Other than knowing it was the code for missfire #3, what esle would the VAG COM have told me?

dave240Z

once I swapped the injector with cylinder #5, the problem showed up as a misfire on cylinder #5.

The problem with mine was that it was leaking. There is no check or sensor that can be made to detect this other than a decrase in mileage and rough running which in turn throws the misfire code if it's severe enough.