Re: ISV Cleaning...

[John Karasaki <johkar@teleport.com>]

At 01:51 PM 4/14/97 -0600, you wrote:
>
>I have twice had my 87 5000S quattro have problems cold starting. It 
>starts up, then stumbles, then stalls. It usually takes a bit of throttle 
>to get it going again after the stall. I thought that this might indicate 
>a dirty ISV, does this sound reasonable? I was just going to take it off 
>and clean it with carb cleaner, is there anything else I need to watch 
>out for?
>
>Thanks, 
>Rob
>
Sounds like a vacuum leak to me.  Try this:  with the car warmed up and
running, pull out the dip stick.  The car should not die.  If it does, then
you probably have a vacuum leak somewhere.

Stumbling when cold indicates a leak of un-metered air causing a lean
condition.  When the engine is first started, the O2 sensor is off-line so
the system can't compensate for that un-metered air entering the system.
The mixture is too lean, so it stumbles and dies.  When it's warmed up, the
O2 sensor is on line and it can compensate for the lean condition by
richening up the mixture, so your car runs fine.  I have this problem on my
urq (as bench diagnosted by Scott M., thanks), but haven't the time to fix
it now that I have the "new" toy.

Good luck. HTH.

Regards,


John Karasaki

Audi Quattro Fanatic