Throttle position sensor/circuitry checking w/resp. to poor fuel econ.

[Jeremiah Curry]

I was getting similar mileage, I had a full tuneup done; plugs, air cleaner,
fuel filter etc. etc. at my local shop and the thermostat replaced at the
same time.  Now I get about 18 mpg around town and 24 on the highway.  Not
sure if it was icremental of if one of the components was bad, but I am
pleased with the results.

-----Original Message-----
From: 200q20v-admin at audifans.com [mailto:200q20v-admin at audifans.com]On
Behalf Of benswann at comcast.net
Sent: Tuesday, September 09, 2003 8:45 AM
To: 200q20v at audifans.com
Cc: quattro at audifans.com; benswann at comcast.net
Subject: Throttle position sensor/circuitry checking w/resp. to poor
fuel econ.


I have been in process of trying to identify cause of poor fuel economy and
mid-
throttle flakyness that has existed in my '91 200 20V tqa before I purchased
it
earlier this year.  Fuel economy at best around 20 highway and 16ish around
town - same type of load and driving in '87 5ktq avant never got under 20
around town and usually 26-28MPG highway.  Also the car seems to "buck" just
a
tad under accel/decel when going on/off throttle.  No problems wih full
power
and car performance is spectacular.

One of the suspects I've been trying to rule in/out is the throttle position
sensor and circuitry.  According to Audi/Bentley Sec 24-120-2 the voltage
between pins 1 and 3 must be 4.5 to 5.5 volts.  On my car the reading was
3.3V.  According to Bentley that means faulty wiring or bad ECU.

Having access to another unchipped '91 200 20V, I ran same test - voltage
between pins 1 and 3 is 3.7V  which is apparently not in spec. either.

Is the manual 100% correct.  Is this a coincidence and both cars have a
problem?  Is there something that goes awry inside the ECU?  I don't see how
this would be wiring as I get a consistant reading and have not found any
signs
of wire damage.

As I continue to attempt to track down what I perceive to be a problem, I am
wondering if this is a common descrepancy.

Not to muddy the waters here are some other things checked/verified:

TPS checks OK/in spec. except resistnce between pins 2 and 3 varies from .9k
to
max at WOT ->2.7k - Recent question from other lister enquired if this is in
spec or not as Bentley not clear, but indicates resistance must increase to
a
maximum of 3600 ohms.

MTFS replaced recently.

New Thermostat.

New Plugs, cap&rotor in good shape.  New Ai filter & MAF sensor clean.

ISV cleaned operating OK.  Vacuum sorted - no air leaks.

No Fault codes.

O2 sensor - unknown, but looks new and notes from PO indicate it was
replaced.

For the moment seeking answer to question regarding TPS connector pins 1 & 3
voltage descrepancy according to Bentley, but invite answers leading to
solving
this latent problem once and for all - apparently haunting P.O. too.

VAG-COM being procured.

TIA

Ben

Rant on - part of the reason for bad fuel economy are the careless drivers
who
just pull out in traffic and don't bother to accelerate and worse put on the
brakes - I live near a retirement community, so this is bad problem.  But
comparing apples to apples, I had the same problem with the '87 5ktqa. -
rant
off.
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