Weird Idle problem. (idle kickdown causes stall on cis-e)

[flaatr@yahoo.com (Euroroc II)]

I replaced the ICM and the knock box, checked the differential regulator 
and vacuum and all the problems remained. Looks like there is a bit of 
carbon tracking on the cylinder #1 too but I was able to work around this 
buy cleaning the inside of the boot... The new Knock box and cleaning the 
plug wires (will replace them soon) made the motor run a lot smoother and I 
gained some lost power, very very noticeable difference (pulls stronger 
than it did at RITF2K2) but the dip in the idle and weird tach reading @ 
around 3K remained so I decided to clean the next piece in the puzzle, the 
Idle stabilizer valve...

I sprayed carburetor cleaner thru the ISV until it was spotless inside, 
then I sprayed a little more just to be sure  :-)  Presto problem gone! 
Seems like there was enough junk in there so the valve could not respond 
fast enough to compensate for the drop. The funny thing is that it worked 
fine at idle... a sticky spot perhaps.

I can now let off the gas in any condition and at any RPM and the motor 
goes to perfect 850  idle!!! The funky Tach problem remains, what else 
could? The only parts I have not replaced are the tachometer itself and the 
ignition coil.

-RGK-



At 04:59 PM 9/20/02 -0400, you wrote:
>The rieger does the same exact thing:
>     our cars have an idle fuel cutout. if the throttle is at the idle 
> position,
>it closes the switch on the throttle body. if the idle switch is closed 
>and rpm
> > ~1600, this results in the jetronic box applying ~-50ma to the DPR 
> until rpm
>drops below ~1400 rpm. This lets the engine coast down with no fuel (as 
>opposed
>to the fuel injection attempting to supply correct fuel during a coast).
>     as a side note, there is a time delay. the ecu must see the idle switch
>closed for >1/4 second in order for it to start the idle kickdown process.
>
>the reason we get our stall is a combination of any of the following:
>
>- dirty idle contact, resulting in longer than 1/4 sec lag for ecu to see the
>switch closed (switch debouncing is accomplished by a r/c circuit in the
>jetronic box), resulting in the kickdown occuring right at 1400 rpm or 
>slightly
>below, possibly resulting in a stall if you get it just right.
>- sluggish/clogged fuel system, resulting in a lag as the DPR attempts to get
>back to normal control pressure (<1400 rpm). if it cant get pressure back 
>quick
>enough, you stall.
>- vacuum leaks (may not be enough to mess with idle, but can be enough to 
>cause
>a stall in this kickdown condition).
>- tuning: the kickdown circuit recovers to the standard +5 to +10 ma DPR 
>current
>range. if you adjusted/tweaked your DPR current out of this range, your 
>fuel/air
>will be out of whack immediately following the kickdown. this may be enough to
>cause a stall.
>- idle speed set screw adjusted too low. if the ISV is already at near max 
>open
>dwell during a normal idle, it cant open any further to correct for the 
>downward
>swing during a kickdown, meaning its harder for the system to recover a 
>low idle
>speed, and you stall.
>
>     and finally, the reason the problem goes away when the a/c is on: idle
>kickdown is disabled with the a/c on to prevent compressor loading from 
>stalling
>the engine during a kickdown event.
>
>     I plan on messing with these things one at a time until i nail it, 
> but i am
>fairly certain that its a combination of the above thats causing it right 
>now. i
>have a feeling simply opening the idle speed set screw a bit will fix the
>problem.
>
>HTH
>Al
>
>Allyn Malventano, ETC(SS), USN
>87 Rieger GTO Scirocco 16v (daily driver, 180k, rocco #6)
>86 Kamei Twin 16V Turbo Scirocco GTX ('it has begun', rocco #7)
>86.5 Occo 16v Trailer (dotting 'i's across the country, rocco #8)
>87 Jetta 8v Wolfsburg 2dr (daily driver, 260k, 0 rattles, original clutch,
>driveshafts, wheels :)
>
>
>----- Original Message -----
>From: "Euroroc II" <flaatr@yahoo.com>
>To: <scirocco-l@scirocco.org>
>Sent: Friday, September 20, 2002 4:45 PM
>Subject: Weird Idle problem.
>
>
> > Heres one for ya...
> >
> > My car idles perfectly, closed loop @ 870 RPM, smooth, stock cam. new
> > distributor & Cap & Rotor, differential pressure regulator & fuel
> > accumulator are new too along with plugs, filter, and oil. The alternator
> > is working fine and the battery is happy, 13.5-14V from alternator, no hard
> > cranking when starting,  etc. etc. etc.
> >
> > When I drive the car and come to a stop, slowing in gear to below 2K before
> > letting the clutch out the engine speed will drop to 500 RPM'ish bog for a
> > split second then return to perfect idle (or lower and occasionally stalls
> > although not that often) . This is repeatable and annoying. Revving up and
> > letting it drop is fine, holding at a higher RPM and letting it drop is
> > fine. the problem only seems to happen when the car is driven, higher RPM
> > under load and let it out of gear under 2K. Letting it out of gear above 2K
> > is good, engine returns to idle without dipping.
> >
> > Strange thing is that if I have the A/C on the entire problem goes away.
> >
> > I've had it in the shop several times, for many days, and they can't seem
> > to figure it out. The problem remains so I ask the group...
> >
> > Anyone have this problem before and how did you fix it? I may have left out
> > a detail or two so ask me any questions you have.
> >
> > -Raffi
> >
> >
> > _______________________________________________
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> > Scirocco-l@scirocco.org
> > http://neubayern.net/mailman/listinfo/scirocco-l
>
>
>
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