clancy

My 2001 A6 2.7 has an intermittent miss on #5 cylinder. Using VAG COM and looking at channel 016 it shows the misses for cylinders 4,5,6 of which only #5 is missing under acceleration. The far right column indicates whether the VAG COM is enabled or disabled. As I let the car idle and slightly rev the motor this column changes from enabled to disabled seemingly on its own. What triggers it to enabled? Why does it count misses for a while and reset to zero? I want to be able to enable it continuously. Can this be done?

Assuming the steps to chasing the cause of the miss is to first swap the ignition modules and see if the miss moves. No it stayed on #5. Then to swap the coils, then the spark plugs. Hopefully it is one of these three options. If not then is it safe to assume it is the injector?

Update, car does not miss when cold or when idling. Only seems to miss on #5 when I am in park and increase the idle to about 3000 rpm, then is misses about once a second. So it counts misses until about 20-25 then resets and starts over. When driving it is the same, no issues until I get over 3000rpm. Then they increase fast as engine stutters, and a flashing CEL. Then it sets a code for random misfire on #5. If I go back to moderating driving the flashing CEL goes out.

Am I approaching this correctly?

uberwgn

Do you know the age of the coil packs and plugs?

clancy

Coils are originals, plugs about 10,000 miles. Car has 200,000 miles.

Harleyguy

At 200k I would have already replaced the coil packs, probably more than once. Many recommend that you change out the coil packs every two plug changes.

uberwgn

Yeah, I totally agree with HD guy on the coil packs. They have a finite lifetime. I think our C6 A6 is on it's 3rd or 4th set at 135k miles. I replaced 3 of them a couple weeks ago trying to chase down a miss that VCDS doesn't pick up. There was a notable difference in the car's performance and the miss is gone. I'm going to order the other three this weekend so the entire set is fresh.

I think these coil packs are a bit of a weak link in the Audi/VW system.

clancy

Swapped #5 & 6 coils and the miss moved to 6. Just ordered a new set of coils.
Thanks

uberwgn

Excellent!

georgeb944

Since I have two high mileage A6 2.7T cars that use the ICM and Ignition Coil setup, I carry a couple of (pre-tested) ones with me, in case I am on a long trip and do not want to spring for the list price on either one. If you are not in a big rush (i.e car is broke down somewhere), original ones can be had for a fraction of the price. The last two ICMs that I bought on ebay were less than $25 each. Ignition Coils about the same price... (Yes, I'm cheap, but all of our cars are running on used parts at this point...)

clancy

Went with ones from FCP Euro. If the replacements go bad then FCP will replace at N/C.

dwengi

At 170,000 miles I have replaced both ICMs once but still on original coils - although I do have a spare coil to swap out when diagnosing misfire.