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

[flaatr@yahoo.com (Euroroc II)]

I've tried opening the screw but first it doesn't help and second the car 
will start to run open loop...  neither is good.

You're explanation is the best I've heard and I think I can lick it... I 
was always curious why the problem disappeared when the A/C was on... is 
there a signal to the Jetronics box for this?

I wonder what box the St. Bentley of Volkswagon manual is in? I hate moving!!!

-Raffi

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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