Ok, so without much practical experience in a problem like this (knock on wood) I'd throw out there a cracked piston ring land or broken rings. What did the boroscope show in that cylinder?

 

How old are the plug wires? I know you checked with an ohm meter but that is low voltage and won't identify high voltage leaking to ground.

The compression and leakdown are well within limits that #6 should fire and run cleanly. You swapped injectors so that's not it. Has to be something else, and a plug with a weak spark would look like that.

 

The borescope I borrowed did not have enough articulation to turn and see the walls after pushing through the spark plug hole. The camera angle was also too narrow. The only thing I could see was the top of the piston. I had the piston all the way at the bottom of the stroke.

I swapped the distr caps, so that is not it. I will see if I can find a replacement plug wire to see if that is it. I think I have my old wires from my S4 somewhere around here.

 

plug wires are new, however during a dyno run the shop owner had one hell of a time getting a clean reading on a run due to interference. He said he hasn't had that much trouble getting a car grounded in some time. Not sure if that means anything.

 

All this happened after a dyno session?

 

Do you think the fouling is an ignition issue? Why?

 

No, it always has had a puff of blue smoke and oil consumption. Just now really tracking it all.

 

Tired a leakdown test with some ATF in the cylinder?

 

found an extra plug wire and fitted it on no6....guess we drive it and see what we see. trying to check everything off the list.

we flipped injector, caps/rotors, changed o2 sensor, fitted AFM gauge, ohm-ed no6 plug wire, and now replaced no6 plug wire, compression test, leak down test, went back to original temp plugs, i think next will be checking TPS & swooping the LH and or MAF.........

 

First you need to check leakdown with some ATF in the cylinder. If the % goes back to the mid single digits, the rings are shot.

 

I'd guess it's a broken ring or cracked ring land or something like that.

Many turbo cars report similar symptoms with cracked ring lands, which then let combustion gasses our during the power stroke and suck in oil during the intake stroke. The reason I'm hesitant to make that forecast here is that (other than my overall inexperience) the 928 S4 ring lands are really, really hard to break. We've tried and they don't want to let go.

 

Or stuck rings. This might be a case where chemical magic works. Add a quart of Rislone and drive it for a month or so. No real down-side, might free up some of the rings.

 

Did the leak check on #6 again today. Today, the test shows 10% instead of 13%. The only thing I can think of is that the engine was hotter today than the last time? I am not sure if that would make that much difference, but that is all I can think of.

I also didn't have any ATF, so I poured some Rislone down the spark plug hole and re-did the test. The leak down number went from 10% to 5%. I don't think there are any issues with using the Rislone. The car is smoking a lot from burning it out, but assume that will pass.

I checked the TPS. I believe it is Ok. Is was showing 0 - 0.1 ohms (manual says

 

(manual says < 10 ohms). The switch goes to infinity as the manual instructs.

I checked the Temp II (it was fine) and cleaned a couple more connectors. Jason picked up the car so we will see if any of that and/or the substitute plug wire makes any difference with the throttle hesitation and plug fouling.

 

I have the same issue with #6 plug fouling a little. It still shows that's it's burning but its oil or fuel fouled. I had the heads redone and put new rings in the engine after I bought the non running car. My guess is a problem with the head(valve spring,valve, valve guide) or damaged piston or ring on mine. It still runs good so I leave it alone. I did put a new injector in there and change out that plug often.