Adjuster

So, I've had a complex year or so with this 2001 S8. I found it down in the LA area, and drove it back up to Boise. On the way home, I had to buy a tire, change the oil, had a low oil scare, the tire shop ripped up the under engine cover, and then the CEL started to flash if I drove it over 120mph.

I resolved the wheel/tire problems, found one wheel with a major bend, one with a minor bend, but only use the stock wheels for snow/winter tires.

The flashing CEL went to a solid light after a few WOT moments, and I had the code for multiple random misfires. I found the fuel pump bolt was stuck, just turns, so I added an external walbro 255lph pump and new filter. I also changed out 4 coils that tested bad per the VAG com.

Still no joy. Still flashes CEL, still drops ignition to one or more plugs depending on how long you stay WOT.

And the toluene in the tank just seemed to make it worse, not better. (However, the tank is spiffy clean when I pulled the level sending unit, and looked inside.)

So, Thursday, go to get my daughter after school, major rain storm, hail and flooding streets, but I was good, did not play in the puddles, and my car was garaged for the most of it. Went out to start it and take her home, and it just cranked.

Long story short, VAG com shows ECU is not talking. Flat bed to local mechanic, says ECU is fried.

Found ECU, and it's on the way now, so I'm really, really hoping that this resolves many issues. This car only has 85,000 miles on it, so should NOT have a fuel pump problem, plugs are new, coils should all be good.

It sure would be nice to find that the CEL and random misfires were just indications of the failing ECU.

Any thoughts?

tozoM8

If you swap ECU you will need to recode the immmobilizer.

audinutt

Yes, you will have to flatbed to audi to have them reprogram, bring all of your keys too. Expect to pay around $150-$200 (might be more since you are in California - the land of everything is expensive)

On the bright side the car should crank, almost start and stall if it indeed was a bad ECU.

-Richard

twentysevenlitres

Can VCDS handle that?

Boise is in Idaho isn't it (says the Australian)

audinutt

VCDS can if you have the SKC's from both cars that the ecus came from (virtually impossible).

I thought he was in california for some odd reason, sorry about that.

Adjuster

UPDATE: Good news is that 116.00 later, the dealer reprogramed the immobilizer, and my keys/fobs to work with the used ECU.

Also good news is that the local shop only charged me 76.00 to diagnose and swap out the ECU.

Had to tow the car twice on flat beds, but the REALLY great news is I work in insurance, so I know my policy. The ECU failed under an electrical storm, the car could have been hit by lightening, or some EMP type spike, or water intrusion, either way, it's a COMP claim. I used my roadside coverage for the first tow, and when the shop told me the ECU failed, it's clearly a comp claim, so I called it in, and picked up a rental car since mine was down due to whatever fried the ECU.

The old ecu was burned/stinky too. Very stinky, but I have not attempted to open it up and see what fried in there. The used ECU was 170.00, the dealer wanted 1200.00 for a new one. The tow bills were 80.00 each. So, the insurance company is thrilled I saved them money by going with cheap shops, cheap tows and a used ECU.

Now for the ECU.

Car starts and runs great. No more flashing CEL, but it's still on solid, and appears that the air injection system is still a problem, but not what killed my ECU clearly.

Could the injector/coil driver be the culprit that finally failed in the big storm we had here? Whatever burned, really went to town, it's not smoke burned, but the ECU reeks if you smell at the plugs.

The best part is no more random misfires. I've tested, and replaced 4 coils prior, but still had the random misfires, and thought the fuel pump was going bad, or a bad coil etc. Turns out it might have been the ECU all along and it just needed that electrical storm to push it over the edge?

Before, if it dropped out coils, it would run rough, but when turned off and back on, would run fine again unless I used WOT more than a few seconds, then it would drop coils, and run rough again.

Now it just is smooth power all the way to redline, and as long as I can stay WOT without running into/over traffic ahead of me.

I have not had a chance to top speed test it, or push the car to sustained high speed runs yet, but expect it will handle it no problem.

twentysevenlitres

That's good news Adjuster! Pleased you sorted it relatively easily...


Well, that explains the username!
I would never have thought to claim on insurance for something like that.
I would have just worn the costs!
You tend to think of insurance as just for road accidents...

Adjuster

Thanks, I'm thinking I spent quite a bit of time and money chasing fuel and ignition problems while the ECU was failing the whole time, and finally died in the storm.

Too bad it' not something you can just check out easy due to the immobilizer feature.