liljoey99

So when it rains or I take the car through the car wash I get the dreaded ECP/ESP and check engine light. Fuel economy drops drastically and the car begins to rev and maintain at about 2500 rpm. So, I connect my VAG clear the codes. Reset all components to factory setting. All is well for about 15 miles of driving in dry condition. Then it rains and BANG, here it goes again. ECP/ESP check engine light. I've read through several posts about the same issues with others. So, I took the car in for vacuum leak check. Audi service shop says NO Leaks. Then, I take it upon my self to change all O2's, Spark plugs, PCV, add fuel treatment cleaner, and take apart then clean throttle body and regulator. ABS control module replaced by Audi 6 months ago (very expensive!). The vehicle goes for about 60 miles (NO Rain, NO car wash, NO problem). It rains, BANG, ECP/ESP and check engine light, fuel economy drops drastically and the car begins to rev and maintain at about 2500 rpm. Now I go through the engine bay with a fine tooth comb, checking to see what is getting WET. Ran it through the car wash, brought it to the bay, put it on the lift, check for what is getting wet that should not (electrical components, ECU etc.) Nothing, all is dry from what I can see.

Left to do:
1. Fuel filter change (on order)
2. Throttle body change (on order)
3. gasoline "burn it to the ground"

Audi A8 USA/CAN 2004>, 2006 (6), Saloon, BGK 4.2 Motronic / 246 kW

Read Codes BEFORE CLEANING THROTTLE BODY REGULATOR
18061 Please check DTC Memory of ABS Controller : P1653 - sporadic 008-Implausible Signal
17976 Throttle Actuator (J338): Mechanical Failure : P1568 - sporadic 001-Upper Limit Exceeded

Read Codes AFTER CLEANING THROTTLE BODY REGULATOR
17950 Angle Sensor 1 for Throttle Actuator (G187): Implausible Signal : P1542 sporadic 008-Implausible Signal
18061 Please check DTC Memory of ABS Controller : P1653 - sporadic 008-Implausible Signal

Any takers on suggestions or comments????

Jack88

Well, for the P1542, I'd suggest checking the angle sensors on the throttle body. Maybe if you can't see anything, spray the area with a water bottle, and if the problem arises, that tells you it's your issue. For the P1653, that's just telling you to check the ABS module for faults, you have to go there to see what it is. Wiring harness degradation is pretty common there.

liljoey99

I have a new throttle body with TSP coming. As for the ABS module, I see no visible degradation in the harness except for normal outer wire cover wear. The ABS code clears with the rest of them and only after I reset the ECU to factory setting. I will update with results after throttle body replacement. Appreciate the suggestions JACK88.

dvs_dave

liljoey99

volvopentaman

Your fault codes clearly tells an intermittent throttle body position sensor problem, or better to say, a mechanical malfunction.

This means your throttle body jams into a position now and then (when it rains), and your ECM has no control over the engine airflow because the throttle plate doesn't do what the ECM wants it to do.

Because of this at times your ECM/ECU doesn't know what position the throttle plate is in, and takes a default position. Driving is of course harsh, and high idle/driving RPM possible because the ECU has no control over engine air flow, and the transmission has to be in a lower gear to keep reasonable speed and driveability. Because of this low gear/high rpm your fuel economy is crap.

You only have one throttle body on the 4,2 engine, so take it off, take off the plastic cover (fastened with a few metal clips) and inspect. Probably gear teeth missing or just debris inside, or the throttle plate axle jammed. Grease or replace if badly damaged or still jamming after greasing.

Have had a few cars with similar problem, dirty throttle body (full of oil fume crap from crank case ventilation) or just corroded from moist air entering engine.

liljoey99

Problem Solved! Every one of you who commented on my forum was exactly right!

Water ingress issue: Check!
Cleaned it all out with 3-foot copper tubing, forced air gun, and shop vac. There were years worth of crap in the drain holes. NO more water pooling up under the cabin air duct.
Throttle body failure: Check!
Received the new throttle body in the mail. Replaced the old one. Found out that the four metal brushes in the TPS housing were bent out of shape and the throttle plate had several grooves in it. NOT GOOD. (I wonder it is salvageable? Is there a rebuild kit I can buy?)

So far the car is sounding and driving very well again. Took it for a 30-minute test drive, and NO codes. And it's been raining for 3 days straight! Fingers crossed, as I take her on an 8-hour journey to the port where she will be shipped back stateside for me. Thanks again all.

I'm happy. Thank you all for your responses and support.