GIdoc

Hi,
My 99 2.8Q(30V) has a weird stalling problem. When I come to stop or at idle the RPM's drop to almost zero, then recovers(or doesn't) and stalls, I have to keep my foot on the gas to keep it from stalling. BUT, If I TURN ON the AC or HEAT THE RPM'S RISE, and the CAR WILL NOT STALL. If I keep the climate control on the car is fine and I can drive normally. There is no hesitation and drives perfect. There is no check engine light on.
The car has gas (chevron), added dry gas, a new battery, a new ground strap, new alternator and belt, new spark plugs, and new oil and filter. I tried to clean the ISV, but couldn't find it! Does the 30v have an ISV? Any help would be greatly appreciated!! If someone has a pic of the ISV could you post it.
Thanks,
TR

Seattle Scott

The guy just in back of the green vacum line.
Located at the rear passenger side of the engine on a 2.8 12valve.

IAC - Idle Air Controller
ISV - Idle Stabilization Valve

IAC is the term in the Bentley manual. Need a cleaning procedure? Email me.

<img src="http://pictureposter.audiworld.com/12414/iacv01.jpg">

2.7tDallas

Could be a vacuum leak. Could be the computer.

GIdoc

Why does the A/C-Heat keep it from stalling?TIA

Seattle Scott

Engine idle is increased to about 1000 RPM if AC is on. W/O AC idle about 650-700.

GIdoc

I have noticed that there are a few frayed hoses on top of the intake plenum(above the ISV), my 30v has the ISV right?

quattro5

no ISV for the 30v - all is controlled by the ECU using the throttle body. vac leaks maybe, but also check electrical connections. also could just need a throttle adaptation to be run if that somehow got out of whack. ECU would have some codes to tell you if that or other sensor/electrical problem exists...

here's a quote from the manual, for reference J338 is the ENTIRE throttle body housing/assembly:

Idle speed stabilization is integrated in the throttle valve control module -J338-. In the housing opposite the throttle valve are Throttle Position (TP) sensor -G69-, Closed Throttle Position (CTP) switch -F60-, throttle drive -G186- and angle sensor -1- for throttle drive -G187-.

The housing should not be opened.

The individual components cannot be replaced or mechanically adjusted. All adjustments are accomplished by the VAG1551 Scan Tool (ST) using the "Basic Setting" function 04.

If the complete throttle valve control module is without power (i.e. disconnected), the throttle valve assumes a mechanical closed throttle position that results in an increased idle speed of 1200-1300 RPM (with engine at operating temperature).

If only the Throttle Position (TP) actuator -V60- is without power, the throttle valve also assumes a mechanical closed throttle position (limp-home position), but because the signal from the CTP switch -F60- can still be recognized, a nearly "normal" idle speed of approx. 900 RPM is maintained with a corresponding reduction of the ignition timing advance.

If the Engine Control Module (ECM) recognizes a malfunction in the angle sensor -1- for throttle drive -G187-, it switches the power off for throttle drive -G186-, and the throttle valve again assumes the mechanical closed throttle position (limp-home position).

2.7tDallas

Figuuuring out what changes to make it idle up will tell you where the problem is

quattro5

which overcomes whatever small defect is hurting the low idle - vac leak or temp sensors or mis-adapted throttle body or.. or.. or...

in the meantime, running the AC is a good workaround - unless it goes below 40, and the AC won't run!

Seattle Scott

Caused the low idle problem. Car ran fine in gear or in Park wih AC on. Loosened up the two bolts for the plenum and rescured it, all has been fine for thosands of miles.

Remember this is all 2.8 12 valve stuff.

Here's the plenum :

<img src="http://pictureposter.audiworld.com/12414/intakeplenum.jpg">