[s-cars] Forwarded for a V-6 List member: Idle Control Problem/Troubleshooting

[Kirby Smith]

Wow!  Where to start.

First.  Replace the rubber hoses that connect to the ISV.  The L-shaped
one usually fails at the bottom.  Be very careful with the straight one
that goes toward the rear of the engine, it connects to a 3-way plastic
part that can be brittle.  This part can also be a cause of an air leak.

Using a power supply, flashlight battery, or the car battery with an
~100-ohm (?) resistor, check that current supplied to the ISV causes it
to move.  If not, get a used one.  Force5 Automotive

The buried screw on the fuel controller is not to set idle speed, but
idle mixture.  Do not adjust without having the Bentley procedure
handly.  Current thru the mixture control has to be monitored and set,
preferably with a mixture measuring device, but if all other parts of
the engine are perfect, just measuring the current is sufficient to
adjust.

The reason for the delay in your problem is that the engine does not use
the oxygen sensor for cold starting, and uses an extra injector.  If
your oxygen sensor is older than 60k miles, you might need to replace
it.  It is possible to test it with an oscilloscope; do you have one?

Include a bottle of Techron with your next fill-up.


kirby  2 x 1988 90q, 1995 S6


CyberPoet wrote:
>
> ********************
> I'm forwarding this because one of you will have the answer,
> and it would seem no one on the V-6 list does (the list is
> not very populated).
> Cheers
> =-= Marc Glasgow
>
> PS - SEND RESPONSES DIRECTLY TO: tomyeyu at yahoo.com
> ********************
>
> Hi, everyone:
> As I now have trouble with the idle control system of
> my car, an Audi 80(not Quattro), manual car,1988,about
> 200k miles, with CIS-E M fuel system, I have to fix it
> by myself due to the high cost of repair by mechanics.
>
> But I don’t know too much my car as a new driver; it
> is highly appreciated if you could give me some
> instructions.
>
> Thank you so much, I really need help from experts on
> this fuel system.
> ____________________________
> Problem:
> High idle speed and not stable
> Once I start the car, tach needle will gradually
> climbs to 1200rm or a little big more than that within
> a few seconds, and then runs steadily at that speed,
> instead of 1000rm(normal idle speed). Then, after one
> or two minutes, the idle problem comes. The touch
> needle (of engine speed) begins to fluctuate
> delicately but frequently around 1200rm, and the
> engine shakes accordingly.
>
> History:
> It appeared about two moth ago, but as I drive the
> car, it seems that the problem gets worse day by day.
> One week ago, I drove for 500miles in two days (have a
> rest in the night). After this long journey, the
> problem gets much worse than before: the problem
> happens every time when the engine is at idle, and the
> touch speed just fluctuates more frequently then
> before.
>
> Discoveries and tests by myself:
> 1.Code dumped
> (1) 2231
> -Location of problem: Idle stabilization control
> limits exceeded
> -Possible reasons: Adjustment of throttle, or, intake
> system leaks, or ignition timing improperly adjusted
> -Solution: Perform throttle adjustment, or, check
> intake system, or, adjust timing
> (2) 2343: Mixture control lean limit /idle NOT
> OK/check idle
> (3) 4431: idle stabilizer valve/ disconnected wire or
> short, or, defective idle stabilizer valve/ check
> wiring, or replace idle stabilizer valve.
>
> 2.Idle screw on throttle body.
> When I turn the idle screw (on the throttle body )
> anti-clockwise, the engine shakes, more turns, harder
> the shake will be. When I turn it clockwise, the idle
> problem will get less worse, but it is a pity that it
> cannot be turned too much, because the screw has been
> already very tight.
>
> 3.Possible problem with wiring routed to ISV.
> When I unplug the harness connector routed to Idle
> stabilizer valve (ISV), it is strange that the engine
> can still be started without any problem, and once I
> plug it in, the engine is not affected neither. Again,
> when I unplug it during the time the engine is at
> idle, the engine is still running.  In a word, nothing
> changes.
>
> 4.About the ISV itself.
> I ever take it off and cleaned it for two times. First
> time, I just sprayed carb cleaner inside it and then
> reinstall it, but it doesn’t work. Yesterday, I let it
> spoiled by carb cleaner for a whole  night. This
> morning, I found that the votary valve inside the ISV
> could be moved if I move it with my singer (it will
> not move last time even if I move it last time).
> Obviously the carb cleaner melts some accumulated
> carbon. But still, it doesn’t work at all after I
> reinstall it.
>
> Besides, when I touch ISV when the car is running at
> idle, I can feel that it is vibrating. So, maybe it
> still works properly, but  I can still feel the
> vibration even when I unplug the wiring connector. It
> is strange. I don’t know how to check whether it still
> works properly or not.
>
> 5.Only after I have started the car for a few minutes,
> the idle problem comes. In another word, during the
> first one or two minutes after I start the car, the
> engine speed is less than 1200rm, but then climbs to
> around 1200rm and begin to fluctuate.
>
> 6.When the idle problem happens, if I switch on the
> A/C, the speed of engine will fall to a lower speed
> (somewhere between 1000rm to 1100rm) and can maintain
> it, no idle trouble then.
>
> 7.Engine shake
> Whatever when I start the engine and switch off it,
> the engine will shake very shortly but obviously. This
> problem has continued for more than one month. I ever
> changed a motor mount but it doesn’t work at all.
>
> 8. The hose routed to intake manifold from ISV.
> Both the hose and the elbow between the hose and
> intake manifold are loose, not so tight. In other
> words, the air can leak from them. I changed the
> elbow, but it doesn’t work.
>
> 9. Hard cold start
>   When the car is cold, I need to depress the
> accelerator to give gas to the car; otherwise, the
> engine speed will often fall and sometimes stop.
>
> 10.Possible intake system leaks
> When the car is at idle, I can hear a kind of noise—si
> si si- like the noise that you spray some thing, or
> like that the gas is injected from a hose, obvious,
> strong and continuous noise.
>
> The original location is from somewhere around ISV,
> intake manifold, or air inflow system, but I am not
> sure where it is exactly from. Besides, the noise is
> through the whole bottom of the car from its original
> location under hood till to the end of the car. I
> don’t know this phenomena is normal or not.
>
> 11.The engine oil is not enough,and I will add more
> asap,but I don't think this is the culprit of idling
> problem.
>
> My questions:
> 1. What lead to the idle problem of my car?
> 2. What should I do if I fix it by myself?
>
> 3. Why can the engine be kept in good idle status once
> the A/C is turned on?
> 4.How to check the wiring connector to ISV and the ISV
> itself? To see whether the wiring works properly and
> ISV still works?
> 5. How to check the vacuum system to see whether the
> intake system is leaking nor not?
>
> Looking forward to your help!
>
> Anthony
> tomyeyu at yahoo.com
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