This sounds exaclty like the other half of the symptoms I had just
before I fixed the worn out green coaxial cables in my van.

I wouldn't be surpised if these cables are bad or about to go bad in
many (most?) vans of this era. The way it was terminated by the
factory, it is almost guaranteed to fail with vibration over time. I
recommend EVERYONE check for this.

One of these two coax cables sends the O2 reading to the main
computer, and the other is  an RPM (tach) reading sent to the idle
stabilizer valve control unit.

The O2 cable going bad will cause the computer to enrich the mixture
to the point where black smoke (unburned fuel) is coming out the
exhaust. It also causes extremely poor (12MPG!) gas mileage.

The RPM cable going bad will cause the idle stabilizer valve to stop
working properly which would cause the symptom you are describing.

The thing is, you wouldn't know they are coax cables. They look
exactly like regular wires except they are a slightly larger diameter.
Both are terminated underneath a rubber boot so you can't see the fact
that there is an outer braided shield that ends before the crimp
connector.

This braid has sharp pointy ends that rub against the inner insulation
and cut right through it. If the braid gets electrically connected to
the inner conductor, the signal is grounded and the voltage is ZERO.

You will find the O2 cable in the same harness that feeds the
injectors on the drivers side. The RPM cable is just above the tranny
or in front of the AFM depending on year of manufacture. Bentley shows
it on 25.54 as part of the check for the O2 sensor and O2 regulation.

I'm very curious how many of these are bad...

Mike Frost

86 GL

> ...would not hold a low idle and kept stalling.  I managed to
> get going fast enough, and all is fine (no bucking or stumbling)---
> but as soon as i decelerated to low idle --around 900 rpm)  van would stall
> constantly. It would crank right back over like nothing wrong, but low
> power, until I could get on expressway.  Then it runs normally -after an
> initial surge or two --to regular power - as long as I am at upper speeds...