Fault codes, Idle problem, Unintended Acc.

[scott.john.mockry@bangate1.tek.com]

Richard,

On the 86-90 5000/200 Audis with Ten valve turbos.
Regarding the problem with the erratic high idle speed. I have also found the same symptoms
to be caused by a defective idle/full throttle switch that has cracked internal solder joints.
The cracked solder joints will intermittently make contact, sometimes just blipping the throttle
will disturb the connections to make it idle normally for awhile. You can test the switch
with an Ohm meter, I have found the full throttle (2/3 throttle) switch portion to also have
intermittent connections. 

You won't know you have a problem with this full throttle switch unless you check the ECM 
fault codes (you must keep the engine running after you test drive the car) the 86-88 1/2 
5000/200 MC turbo engines (single knock sensor) don't have a fault code memory after the car 
is shut off. The 88 1/2 to 90 dual knock sensor MC engine DOES remember the fault codes 
after the engine is shut off and the fault codes must be cleared from memory. 

I found that I had  a defective knock sensor (Cyl 3,4,5) on my 89 200TQ when a friend hooked 
up his VAG scan  tool. Some of these cars had the "CHECK ENGINE" light bulb removed 
(like on my car) so I  didn't know that one of my knock sensors was bad. My gas mileage 
and power was down because the ECM backs off the timing whenever it detects a defective 
Knock Sensor! The 86-88 1/2 MC engines with one Knock sensor should turn on the "CHECK 
ENGINE" light if the one knock sensor is bad. You can also use the Check Engine light to flash
out the fault codes on these 86- 88 1/2 MC engines. The 88 1/2 -90 MC (dual knock) sensor
cars use 3 connectors under the dash to access the fault codes. You can hook up an LED with
a 12K ohm resistor in series across two of the connectors to blink out the fault codes. If anyone
is interested I can send them the details of connecting this LED.

Scott M.

>From: "Richard J Andrews ,JR." <rjandrew@post.cis.smu.edu>
>Date: Thu, 18 Apr 1996 22:52:42 +0000
>Subject: Unintended Acceleration

>I have just finally determined what cause the unintended acceleration 
>in the '84/'85 model 5000's. I have run across this problem several 
>times and it is the idle stabilization relay that is located down by 
>the relay panel underneath the steering column. TEXT DELETED>
>My GRAND conclusion, 
>you have a problem when your car wants to go and you don't , 
>change your idel stabilizer relay, should fix it!
>Later,
>Rich Andrews
>(Audi Mechanic in Training at Home)