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

[amalventano@sc.rr.com (Allyn)]

sweet. i'm headed out to spray some carb cleaner on the isv in the rieger. its
doing exactly what yours was (i.e. perfect idle).
thx for heads up man
Al

----- Original Message -----
From: "Euroroc II" <flaatr@yahoo.com>
To: "Allyn" <amalventano1@comcast.net>; <scirocco-l@scirocco.org>
Sent: Monday, October 21, 2002 2:07 PM
Subject: Re: Weird Idle problem. (idle kickdown causes stall on cis-e)


> 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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> >
> >
> >
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