re. 88 80Q, Runs rough upon starting

[Ben Swann]

Odds are it is either the Fuel Injection Temp Sender (Neg. Temp. Coefficient
Resistor) located on cooling neck, or the Oxygen Sensor failing and sending a
false reading.  Disconnect O2 sensor and see if problem clears.  Codes are not
necessarily displayed for either of these devices.

 

Ben

http://www.gtquattro.com

 

[Date: Mon, 13 Nov 2006 23:18:19 -0500

From: "Eric Huppert" <dragracer at netstep.net>

Subject: 88 80Q, Runs rough upon starting

To: "'quattro at audifans. com'" <quattro at audifans.com>

Message-ID: <JMEMJCJGJPAPJKLMIMIIEEFECAAA.dragracer at netstep.net>

Content-Type: text/plain;     charset="iso-8859-1"

 

Gentlemen,

 

Have two perspective buyers coming to look at my sons car, and a "new"

problem has surfaced. (new to me, my 17 yo doesn't tell me these things

until he thinks of it, or I ask!)

 

If car is allowed to sit 5-10 minutes after shutting off, (or even on a cold

start) upon restart car fires, then starts to stumble and drop RPM's.

Feathering gas pedal, etc, doesn't help. But, discovered that full throttle

will get the rpm's up, but when let off it still runs rough. It clears up in

a minute or two, but something's not quite right

 

Troubleshooting to present:

 

Car is tuned up, no vacuum leaks, ISV functioning and clean. Not a fuel

leakdown issue (check valve), not the FP. (BTDT several times with other

Audis)

 

Ran codes. Initially no codes, but do get full throttle code when throttle

is fully opened.

 

      So, checked switch (both full and idle portion) according to Bentley.

Voltage specs are good, Ohm check works out for both switches.

 

Air plate clean and moves smoothly, etc. etc.

 

Then on to the Control pressure actuator. Following Bentley, getting correct

voltage to unit, but upon following procedure and checking for 10ma/100ma

(utilizing digital meter) I only get the 10ma. Opening throttle fully

doesn't change anything (as it should per the manual)...

 

The Bentley is just tad vague... My interpretation of the Bentley CPA test

is "voltage is good, WOT switch has no effect, replace CPA! I'm also not

getting decent ma readings when car is running.

 

Thoughts, BTDT???? Sure this is a sensor issue of some sort and can, (and

will) be easily fixed. Need to resolve this quickly!

 

Cheers, Eric]