Once more into the void - 5ktq high 'idle' - update

Ben Swann benswann at comcast.net
Thu Oct 26 23:05:12 EDT 2006

You have confirmed that 

1) there is no problem with the ISV and it is operating as it should 

2) there is a problem with the idle switch or wiring from the switch to the

3) It is not likely to be the ECU itself - things are working as expected.


Don't bother pinching the hose - it will tell you nothing more about the
problem, only that it will confirm (1).


You need to cut to the chase and trace your wiring.  I have found broken wires
on multiple instances, particularly under the rubber boot that covers the
wires at the connector.  Also, the switch may be good, just out of adjustment
- very common. When you move the throttle to open slightly, do you hear a
definite "click" and another "click" when letting it close?  Is it consistant?
If not, try adjusting the switch assembly - loosen two little screws on the
side and turn the switch.  Tighten it up when the adjustment is correct.


I assume you have already verified the switch is good.  You may want to make a
little test connector for checking switches and sensors.  I get ones from a
parts car - plenty floating around in junkyards - two prong for temp sensors
and valves, 3 prong for this and other three prong devices.  It helps in
providing a connection to the switch, esp. when it is hard to get VOM probes
down there.


Failing that, address the connections at the ECU and perform continuity checks
on the wiring to confirm which wire is bad.  A simple loopback from ECU pins
(ref. Bentley and/or http://www.gtquattro.com/MCWiring.html) out to the switch
connector (use a paper clip to make it loopback) and confirm you have a
continuous circuit round robin.  Then isolate the broken wire when you find
this is not the case.


You can methodically isolate this problem inside of an hour with VOM and some
pins - collect some little test goodies to help isolate problems like this.
You can get a cheap VOM from Harbor Freight or one that beeps for continuity
test from Radio Shack - I must have about 8 of these things.  Of course you
have a Bentley with wiring diagram to follow where things are - correct?  If
not, get one - they pay for themselves every time you use it.


You are on the track - the hardest part of fixing these sort of problems is
finding them.



www.gtquattro.com <http://www.gtquattro.com/> 



[Date: Thu, 26 Oct 2006 10:20:25 -0700

From: Fuzzzydog <fuzzzydog at gmail.com>

Subject: Once more into the void - 5ktq high 'idle' - update

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


      <6fdb9b1f0610261020h5a0ab138uc0cb29518047bd95 at mail.gmail.com>

Content-Type: text/plain; charset=ISO-8859-1; format=flowed


Really,guys, I can't thank you enough for the suggestions and pointers.


I had a chance to get out there last night and poke around a bit and here is
one thing I found


as suggested by Ben, I pulled the isv connector with the car running and the
idle dropped - a bit low but very acceptable.  plugged it back in and no
change in idle, went for a drive and the problem was gone - it came off high
speed, down to a low idle at all times.

got home, shut off, restarted and zoom - 3k rpm with no throttle....



So - conclusions?


1.  The ISV is working - doing something - just not doing it right.

2.  The culprit is in the ISV circuit somewhere...  I'm starting to think ECU?


I'm still looking at some of the other suggestions and will check them out (it
gets dark kind of early these days - will be even worse next week when we go
to DST) as time allows.


one thing I wonder about is how the heck do you guys 'pinch off' the ISV
hoses?!?!? they are too hard to pinch off with fingers alone and I am worried
about damaging with pliers....]

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