86 5KTQS High Idle Problem (and others) REPLY

Thu Oct 24 12:44:53 EDT 2002

Hi Ben,

Thanks so much for the detailed response, I will begin the tracing program
tonight starting with the boot and will post again once I have checked
everything as per youre suggestions.

I also had a gander at youre website and particularly liked the boosting
section.

My car has a chipped ICU as I managed to get a rain leak into the standard
one, and having thought that I had the engine worked out and functioning
correctly I thought it was time to try it out (and very nice it is too). I
will post some further questions regarding boost mods once i have solved the
current issues I am having.

Many thanks again

Haydn Taylor

>From: Ben Swann <bswann at worldnet.att.net>
>Reply-To: "bswann at worldnet.att.net" <bswann at worldnet.att.net>
>To: "'haydn_taylor at hotmail.com'" <haydn_taylor at hotmail.com>
>CC: "'quattro at audifans.com'" <quattro at audifans.com>
>Subject: 86 5KTQS High Idle Problem (and others)
>Date: Thu, 24 Oct 2002 10:38:48 -0400
>
>Yes we have and it can be caused by numerous things - sorry about the
>length of this.
>
>Some things I have found, having been through this frequently on 3 out of 3
>5000 turbo quattros in 4 years.
>
>- WOT switch/circuit failure would cause a high idle.
>
>- A failure in the wiring to the Stabilizer will cause RPM to drop/engine
>stall
>
>- A failure in one or more the temp sensor/wiring will cause RPM to
>drop/engine stall
>
>- The decel valve opens by the switch and closes at 1200 rpm - allows the
>plate to
>settle to the rest position. You can actually hear it open as rpm winds
>down.  This could kill the engine..would not start troubleshooting here.
>
>- Check under rubber boots on what looks like good wires to suspected
>switches/valves.  This is especially relavent if you just got finished
>doing some work around the connector.
>
>- Bently wiring diagram  - invaluable, but sometimes hard to follow.  A
>thin horizontal line running through several wires with circle next ot it
>is a welded wire connector - wires are connected, likely share a common
>source.
>
>See below for more extensive explanations and embedded comments.
>
>Ben
>
>[From: "Haydn Taylor" <haydn_taylor at hotmail.com>
>To: quattro at audifans.com
>Subject: 86 5KTQS High Idle Problem (and others)
>Date: Wed, 23 Oct 2002 17:38:43 -0400
><snip>
>Towards the end of last winter I noticed the idle speed creeping up, then
>spring came and the problem seemed to dissapear. As the outside air temp
>has
>begun to decrease again the idle problem has returned. The car now starts
>up
>from cold with a normal(ish) idle of about 1200rpm, as the motor warms this
>builds to approx 2000rpm. When I then drive and stop again, the idle is at
>about 2200rpm, it then hunts up to approx 2600rpm, then after approx 5
>seconds drops back to 2200rpm, this cycle then continues, after a couple of
>minutes the idle will sometimes fall back to about 1800.the thing that is
>really getting me confused is that if I slip the clutch to bring the engine
>down to say 800rpm, sometimes when I fully depress the clutch again the
>idle
>will stay down at 1000, and other times it will go back to it's hunting
>game
>up at 2200.
>
>I have noticed the problem is noticably worse on cold days.
>
>I have also noticed a puff of white smoke on startup that is getting worse,
>and a drop in fuel economy - making me think about leaking injectors (I
>bought a new set at the weekend but have not fitted them yet)
>
>**** this will cause hard starting, but not idle problem ****
>
>My only other thoughts for the cause are
>A. Oxygen Sensor dying  **** NO  ***
>
>B. Temperature sensor somewhere not functioning correctly -  *****remote
>possiblility  ****
>
>C. Vacuum leak somewhere -  ****** Possibility  *******
>
>finally the only other thing I have moticed that is odd and sort of relates
>to the heater controls. with the heater set to 'econ' the idle is a little
>lower (1800 ish), and with it on max, the AC clutch kicks in for about 2
>second duration every 10 to 15 seconds, and the idle is even higher.
>
>**** heater/AC deals with Idle, but not likely problem ****
>
>Any thoughts on this would be greatly apprecated before I start tearing the
>thing down again next weekend.
>
>Yours most sincerely
>
>Haydn]
>
>OK here is a recap for this problem, since it has not been discussed in
>awhile, and not in recent archives probably -
>
><Beginning of recap on High Idle Problems troubleshooting.>
>
>Greetings,
>
>I only got replys from one lister on this.  I sure would appreciate some
>additional help based on experience, esp. with the 5KTQ.  We can rule out
>the throttle body (idle/WOT)switch.
>
>**** NOTE: I replaced the switch, even though the old one checked out fine
>
>**** NOTE:  Switch is the among the first things to check
>
>I dont have the Bently on me right now, but a part of my confusion may be
>the way the diagram shows the wires going to the idle/WOT switch and other
>sensors including the decel valve.  The diagram shows a thin line going
>across two or three wires at a time in several places esp. coming of around
>the ISV conrol unit and also the switch and associated wires, in adjacent
>current tracks.  It is unclear whether this means the wires are actually
>connected, or this is just representing that they a collectively part of
>the same part of a harness.
>
>**** I was on the right track here, but is was far simpler
>
>Is the decel valve know to cause this kind of madness.  Is the +12V  that I
>don't get at the idle switch supposed to be coming from the decel valve, or
>is it the other way around, and I should be looking for a breakdown
>somewhere else.  I'm poring over the Bently manual and see several tests,
>but some guidance as to exactly where to resume troubleshooting could save
>  much time.
>
>So I therefore greatly appreciate input from someone who may have been
>through this already, and/or has a thorough understanding of the ISV system
>and can steer me in the right direction.  Once I get this resolved, I will
>gladly post results of what may be a compound problem.
>
>TIA again.
>*************
>Recap of problem below with additional info as I progress with
>troubleshooting..>>>
><SNIP>
>I just got back from a 3 week vacation in Peru - <SNIP> still chasing high
>idle problems on both cars.
>
>'87 5000 Turbo Quattro Wagon idle has progressively worsened.  Idle after
>warmup ranges from 1200 to around 2200, holds fairly steady and will slowly
>drop down to 1200 - 1500 RPM.
>
>To recap details on symptoms:
>
>I dont believe there are any airleaks, as I've been over this engine
>thouroughly.
>
>I noticed if I force the RPM to drop by putting in gear and loading the
>engine, it will hold the lower idle(somewhat), but will generally bounce
>back up to around 1200RPM if forced to lower RPM.
>
>Idle/WOT throttle switch OK/Questionable(REPLACED), but  bypassing = no
>difference.
>As suggested, I replaced the Throttle position switch(replaced because
>readings were more like 10-20 ohm rather than 0 ohm on switch closure, and
>some perceived flakyness) on the 5000TQ to rule it out, and as suspected it
>made no difference at controlling idle (may have improved possible WOT
>operation however).  SWITCH OPERATION VERIFIED
>
>There is NO VOLTAGE to pin 2 on center connector.
>According to Bently, if no 12V then check wiring.  Referred to wiring
>diagram and confirmed there is voltage at Idle control unit terminal
>15/SAS.
>As I mentioned in previous post, THERE IS NO 12V on the connector pin to
>the switch, but the control unit is providing 12V at the appropriate pin at
>the relay panel, and when the switch closure is simulated, there is no
>difference, and that there is no voltage to the switch when ignition on, as
>specified in Bently.
>
>**** NOTE:  This methodical toubleshooting is good in that it will
>ultimately lead you to the answer in time, but sometimes you end up
>regretting tearing things apart, especially when the culprit is right in
>front of your nose.
>
>Bently diagram shows(if I read it correctly) this goes to the Decel Fuel
>Cutoff Valve first then voltage goes to the throttle switch connector pin
>2.  There is voltage going to the connector to the decel valve.
>
>I pose these questions again in hopes someone has dealt with it: Is the
>decel valve the culprit?  Should I check something else?
>
>It is a pain to get to (and very expensive at dealer), and I don't want to
>purchase new one and pull out the entire FI assembly without reasonable
>certainty it is the problem.  Doyt Echelberger mentioned it was accessible
>from under the wheelwell, which I can try, but still it is an expensive
>part.  I already did shotgun troubleshooting with the throttle switch.
>
>Any BTDT on this.  Any clarification on how the Idle stabilization circuit
>works(is supposed to work), esp. with resp. to decel valve, would be
>helpful.  The system seems to be in some type of feedback loop state where
>the higher the idle is after taking out of gear, the higher the idle stays,
>eg. if I drop the idle to 1200, it will stay there.  Can't seem to get it
>any lower than that after warmup however.
>
>Also, if I disconnect ISV momentarily, Idle drops to 500ish and stays there
>when reconnected which I understand is Normal.
>
><snip> Sorry about the long post - just trying to give a thourough
>explanation of symtoms and diagnosis thus far.
>
>Ben Swann
>
>*** AND THE ANSWER was  ****
>
>-----Original Message-----
>From:	owner-quattro at audifans.com [mailto:owner-quattro at audifans.com] On
>Behalf Of Swann, Benjamin R.  (BSWANN)
>Sent:	Monday, February 14, 2000 9:21 AM
>To:	'quattro at audifans.com'
>Subject:	RE: High Idle problems ..5KTQ - solved
>
>It turned out to be quite simply the wires going to the connnector at the
>ILDE/WOT switch were broken.  I should have checked under the connector
>rubber boot in the first place, but I guess these types of problems always
>seem trivial once they are fixed.
>
>Wiring diagram prompted me to look for this, as the center conductor of the
>connector should be 12V coming directly from the Ignition circuit.
>
>Car idle nice now - solid 750 RPM.
>
>Lesson learned - the wires at the connectors can fatigue and fail which is
>not evident unless you peel back the ruber boot covering the wires. on
>mine,
>three out of four wires were disconnected/broken.
>
><End of recap on High Idle Problems troubleshooting.>
>
>Now with all of that regurgitation, I have found the most common culprits
>to be:
>
>1 - The Idle Stablizer Valve
>
>2 - The WOT/IDLE switch located on the throttle body
>
>3 - The idle screw located on the throttle body (air leak due to hardened
>o-ring)
>
>4 - nebulous anomolies which coincide with position of the moon, and
>sunspots ( things like partial ignition switch failure and the broken wire
>at the switch)
>
>Hope all of this helps.
>
>Ben

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