High Idle 5000 turbo quattro

[Ben Swann]

Your symptoms indicate a problem with the idle switch or circuitry.  Did you
peel back the boot of the connector to the switch to ensure there are no
broken wires there.  Is the switch closing consistently?  Do a full check on
the wiring - continuity check at the ECU harness -  connector pins 20 (+ to
idle switch), and a ground pin: 18, 9 and /or 23: see
http://www.gtquattro.com/MCWiring.html for more wiring info.

 

Pull the ISV connector - idle should drop and not pickup when reconnected
until the car is restarted.  If that is not the case then the ISV itself is
suspect.

 

Often it is a combined problem.

 

Ben

http://www.gtquattro.com

 

[Date: Tue, 24 Oct 2006 10:29:27 -0700

From: Fuzzzydog <fuzzzydog at gmail.com>

Subject: Once more into the void...- does someone have a flashlight?

To: quattro at audifans.com

 

Hello all, been away for a while since I picked up a 4X4 and returned to my

offroading passion, but the 88 5KTQ avant has lured me back.  Unfortunately

it is a love/hate relationship.....:(

 

It is a sweet car - for the most part been running very well since I've

owned it.  But recently I have developed an intermittent high idle that is

defying all efforts to fix.  I have read SJM and other sites and done a lot

of checking.  Right now I am considering different types of rope for a noose

to put myself out of my misery.  Before I go to that extreme, I am hoping

someone can point out what I have missed....

 

Symptoms:

 

MC engine, turbo, 5 speed, all stock - no mods.

 

starts up very well, idle a tad high but slowly starts fluctuating and

getting higher as it warms up.  go for a drive and now it won't come off

high idle - ie coming to a stop, push in the clutch and rpm stay at about

3k.  sometimes, only sometimes, I can let the clutch out to bring the rpm

down and they will stay down right around 800. this is rare though - usually

I sit there at the stop light with the engine doing 3k rpm.

car does not stall when oil cap is removed - even when idle is ok

always, ALWAYS, filled with Chevron super supreme - problem has persisted

over many fill ups

high speed is not affected - done a consistent 140km/hr trip recently -

pulls like a freight train.

oh yeah - this might be important -  when the high idle problem is there,

and I am coasting along at any speed, if I let my foot right off the gas it

keeps motoring along (because of the high idle) BUT, as soon as I give it

some gas to speed up there is a 'dead spot' right off idle.  The car bucks a

bit as if fuel or spark were shut off, then it picks right up and away we

go.  this dead spot is not there when the high idle problem is not present

(remember, the problem is intermittent)

 

things I have done.

checked idle switch - opened, resoldered, tested - all good

replaced ISV with one that came out of a properly working car

checked for broken vac hoses - all good that I could see

checked idle controller under dash and saw that 1 wire was broken completely

apart - fixed - no love - didn't cure the problem

battery is new MFTS is brand new 3 wire swapped the small single wire temp
sensor at the top front of the engine.

checked wiring/hose connections - nothing stood out.

 

Willing to listen to any and all suggestions I have lots of spare parts that I
can swap out from a previously good

running 5ktq sedan.

 

Thanks for reading and looking forward to your input.]