At 10:59 PM 10/3/00 -0400, Phil Desmarais wrote:
I am trying to determine the cause of low RPM
idle at cold start.
My 86' 928S automatic starts fine, but the
idle is only running between 600 and 700 RPMs when cold. When the
engine reached normal temperature, the idle increases to between
1100 and 1200 RPMs.
Is there an idle control component
controlling this or is this a function of the computer? Can this cold idle
RPM be increased without effecting the normal temp idle speed?
Can some one walk me through some diagnostic steps to determine what is
causing this?
Thanks in advance, Phil, PCA member
1998126538
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Your car has an idle control system that should control the idle speed hot
or cold.
In your case, the cold idle speed is correct (spec is 660 - 700) and the
hot idle speed is too high. It is possible that the idle speed has been set
improperly.
To adjust the idle speed:
Warm the engine.
Look on the top front of your engine, just under the cross-bar and just
behind the oil filler cap, and located a round black plastic cap. Carefully
remove this cap (which may be brittle) to uncover three wire connectors.
They are usually arranged with one on the right and two on the left (as you
face the plug).
Connect the single connector on the right to the top connector on the left.
This temporarily kills the idle speed controller.
The idle speed control screw is located on the throttle housing (not the
mass air sensor!) down under the intake pipes. Adjust idle speed to 660 -
700 RPM.
Remove jumpers, close cap.
Wally Plumley
928 Specialists
================
As Wally points out you have a high idle problem , it is possible that the
idle adjustment bolt is set incorrectly but 99.9% of the people have no idea
that there is one for the 85/86 USA car . If the stabilizer valve is not
working correctly the car usually stalls , too low a speed not too high .
The next most likely problem is a vacuum hose leak , intake gasket, charcoal
canister y-connector broken . I would look for some other problem that is
allowing air to enter the intake in a sufficient quantity that the idle
stabilizer can not shut down far enough to hold the correct , approximately
800 RPM idle .
Jim Bailey
=============
At 02:41 PM 11/28/00, Carl D. Kester II wrote:
Please help,
I have a 1998 S4. When car sits for awhile I have to crank engine numerous times waiting in between before it gets gas and starts. Acting like air in gas lines I just replaced the check valve
on fuel pump. After car starts it runs fine. Please help.
Carl
------
Hesitation to Start - '92 GTS
My 92’ GTS hesitates a bit to start. Both from hot and cold. I need to push the
accelerator for it to start. When I push the accelerator it starts right away...
reply:
If you have to press on the accelerator pedal to get it to start, that means
it could be over-fueled at start-up. Potential causes off the top of my head:
- pressure dampener or regulator diaphragm broken thus allowing pressurized fuel
to squirt through the vacuum lines and into the air guide.
- leaking injector(s)
- wrong type of injector
- LH on the way out (if original un-rebuilt.)
reply:
checked Temp2 sensor, which is fine, swapped ecu, no difference.
Solved:
Connected the mightyvac at the dampers and the fpr. Dampers fine. Fpr leaking.
Changed fpr. Sorted. Starts perfect again now.
----
The 1998 models are notoriously hard to crank. ;-)
The 928 must have close to normal fuel pressure before it will crank.
The 928 fuel pump runs for only about two seconds each time you hit the
starter until the engine cranks. As soon as the engine cranks, the pump
runs continuously.
First:
Have someone hit the starter while you kneel down by the right rear bumper.
Listen very carefully for the buzz of the fuel pump. If the pump buzzes for
1 - 2 seconds each time the starter operates, that is as designed. If the
car cranks after the third or fourth time you hit the starter, it is likely
that you are losing fuel pressure.
There are several possibilities here:
1) Fuel pump check valve.
2) Fuel pressure regulators, dampers, etc. may be leaking.
3) Injector(s) may be leaking.
Pull the vacuum line from each fuel pressure regulator and see if there is
any trace of fuel in the vacuum line. If so, the affected unit should be
replaced.
There are other possibilities and other tests, if you feel capable of
getting into the system.
Wally Plumley
928 Specialists