cparke

1998 Audi A4 Quattro V6 30V (AHA engine)

I am told after shutting off the engine, smoke was seen coming out from under the hood, but I wasn't there and my wife of course refused to open the hood so I could get a clue as to where it was coming from. The car did not overheat, oil and coolant levels are fine, all instrument cluster dials were reading normal. Car had been on highway but was being driving locally immediately prior to the incident.

When I got to the car, no smoke (though a faint smell of unburned fuel in exhaust smoke), here is the VAG-COM fault codes I got:

Address 01: Engine
Control Module Part Number: 4D0 907 551 AH
Component and/or Version: 2.8L V6/5V MOTR AT D01
Software Coding: 06251
Work Shop Code: WSC 06335
9 Faults Found:

17549 - Load Calculation Cross Check: Implausible Value
P1141 - 35-10 - - - Intermittent
17746 - Camshaft Position Sensor (G40): Open or Short to Plus
P1338 - 35-10 - - - Intermittent
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-00 - -
16685 - Cylinder 1: Misfire Detected
P0301 - 35-00 - -
16690 - Cylinder 6: Misfire Detected
P0306 - 35-00 - -
18014 - Rough Road/Engine Torque Signal from ABS: Electrical Malfunction
P1606 - 35-00 - -
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-00 - -
16685 - Cylinder 1: Misfire Detected
P0301 - 35-00 - -
16690 - Cylinder 6: Misfire Detected
P0306 - 35-00 - -

Readiness: 0000 0000


Clear the codes, restart the engine, car runs fine, drove it home (including with highway and local driving) without incident, no codes present when I pulled into the garage.

Background: This car has been running with a rich (but not too rich) multiplicative fuel trim problem on Bank 1. I have been suspecting that the fuel injector for cylinder 1 is bad and the cause that problem, but haven't had a pressing need to possibly change it without a CEL until this incident just suddenly happened. Car recently had new coils, wires, and spark plugs installed, so that shouldn't be the cause here. The cause of my engine problems has been very elusive.

The first 2 intermittent fault codes have been sitting in the ECU without causing the check engine light to go on at all for 3 weeks prior to this incident. Those codes were in there when I took the car back from a repair shop which didn't know what it was doing and wanted to change my MAF after I already had changed it myself.

Fuel trims in measuring block 32 were last logged 6 days ago as follows (unfortunately, I didnt re-log them after this incident before resetting the ECU):

Group 032: O2S control learning values (before Cat. Conv.) [B=Bank S=Sensor]
-0.8 % @idle B1S1 +/-10%
-10.2 % @part B1S1 +/-10%
-3.1 % @idle B2S1 +/-10%
-0.8 % @part B2S1 +/-10%


Now, the part that most puzzles me most about this incident is how/why the misfire also happened on Cylinder 6. Cylinder 1 didn't surprise me, I've seen misfires on that one and elsewhere on bank 1, but this is the first time I saw both cylinder 1 and cylinder 6 misfire together, and this happened completely out of the blue without any warning or clue (car was running great just prior to the incident, as well as immediately after, there was no CEL on prior to the incident). Any thought on how a bad cylinder 1 fuel injector could somehow cause cylinder 1 and cylinder 6 to simultaneously begin misfiring together? Is there something else that could explain this bizarre incident.

Finally, is my car wired correctly? On the right (passenger side), cylinders 1,2,3 are plugged in from front to back (cylinder 1 towards front of the car, cylinder 3 towards the firewall). On the left (driver's side), cylinders 4,5,6 are also plugged in from front to back (cylinder 4 towards the front of the car, cylinder 6 towards the firewall). On the coils, cylinders 1 and 6 are connected on opposite ends of the same coil paired section (I can check the other two sections if you think it is important).

Much appreciation for your thoughts. I sure would like to nail this engine problem once and for all.


P.S. We drove the car some more now, and the misfires happened again on the local travel section! This time, the car started shaking and the CEL started blinking for 20 seconds, then it stopped shaking and CEL is steady. Whatever is wrong is at least happening more regularly now, but it still goes away too! I will VAG it when they get back home, but I'm pretty sure cylinder 1/6 misfiring are the problem again.

@wesome

plug wires go into

cparke

2.8L doesn't have one. The coil pack and wires are fairly new.