llonman

I have a 99 A6 with the 2.8 and 144K. I had the same problem about 12K miles ago. The original post is below.
https://forums.audiworld.com/vag/msgs/6664.phtml

I did not get any responces from the VAG forum which is dissapointing as AW has always been such a great asset.

The problem just went away on its own..I fixed my fuel supply lines, changed the oil, spark plugs, and replaced the air cleaner.

The car has been running fine and last night on the way home it started hesitating again. I pulled the codes and it seems to be the same problem.

VAG-COM Version: Release 311.2-N


Chassis Type: 4B - Audi A6 C5
Scan: 01,02,03,08,15,16,17,35,36,37,45,55,56

Address 01 -------------------------------------------------------
Controller: 4D0 907 551 AH
Component: 2.8L V6/5V MOTR AT D03
Coding: 06252
Shop #: WSC 02325
4 Faults Found:
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-10 - - - Intermittent
16685 - Shareware Version. To Decode all DTCs
P0301 - 35-10 - Please Register/Activate - Intermittent
16684 - Shareware Version. To Decode all DTCs
P0300 - 35-00 - Please Register/Activate
16685 - Shareware Version. To Decode all DTCs
P0301 - 35-00 - Please Register/Activate
Readiness: 0000 0000

It seems to be missing on cylinder one only. It definetly drives like it missing a cylinder.
Is there a way to check the oxygen sensor, the the coilpacks, and fuel pressure? I dont think its a fuel problem because if the trim was off it should effect the entire bank of cylinders. Correct?

Thx,

Lonnie

Ernesto (ERT)

<ul><li><a href="http://search.audiworld.com/index.html?q=16684&amp;cat=010033&amp;p=1">Got 38 hits... don't know if they apply to your situation</a></li></ul>

JoeVane

* Corrective Action

1. Fuel level too low, check fuel level and add if necessary

2. Check misfire detection ==&gt;
http://www.wavenetmx.net/misfire.pdf

3. Check fuel injectors ==&gt;
http://www.wavenetmx.net/injectors.pdf

4. Perform output Diagnostic Test Mode (DTM)
http://www.wavenetmx.net/dtm.pdf

5. Check engine speed (RPM) sensor -G28- ==&gt;
http://www.wavenetmx.net/enginespeed.pdf

I hope it helps, if you need anything else from the manual just let me know.

Good Luck<ul><li><a href="http://www.wavenetmx.net/16684.pdf">VAG Codes...</a></li></ul>

llonman

Thanks for the info. I will check the wires and fuel injectors as per the links you provided. I did switch the spark plugs and cylinder one still misfired. Does anyone here agree that if the O2 sensors were bad or the fuel trim was wrong that more than one cylinder on the bank would likely misfire?

Li3ny

I'd check those out. I just replaced mine 1&amp;4 were bad. (100k) They seemed to get worse as the weather got warmer...either that or they just progressed that way. I've thrown plenty of O2 sensor codes so I think you'd get one of them if that was the issue. Swap your coil packs and see if it still misses on one. Mine started w/ 1, then 4 started logging right before I replaced them.

llonman

Thanks for the suggestions everyone. Following the instructions that JoeVane sent I checked the ignition wire and coil associated with cylinder one and all checked out okay. I then removed the fuel injectors and checked the resistance on the injector for cylinder 1 and it also was within spec. So, I swapped the injector from cylinder one (cleaned it with carb cleaner) to cylinder three and cleared my codes. Started it up in the garage and let it idle. Seemed a little better last night, this morning it started missing again. Need to pull my codes and see if three is missing now. I assume if three starts missing, the injector is clogged or something. If one still misses after swapping injectors, I am at a loss. :--(


Lonnie

llonman

I checked most everything I could. Spark plug wire, coil packs, injectors..All were within spec...Switched injector from cylinder one to cylinder three. Still stumbling and I pull the codes and the same codes come up. 16684 and 16685. I guess I need to take it to someone who knows more than me. :--( I must be missing something, no pun intended!