Mike,

         The 'slightest bit of throttle' issue may be significant...

         There is an 'idle switch' located under the throttle body, which
(when adjusted properly) changes state at the *slightest* throttle
pressure. This takes the van from 'idle state' to 'running state'.

         At 'idle state', the Idle Stabilization Unit (electrical, on the
left side of the engine bay) and Idle Stabilization Valve (vacuum operated)
are active, and are supposed to keep the engine idling smoothly. Once you
give it a bit of throttle, this system is taken out of the equation. Sounds
like you may have a problem in that system.

         I recommend you break out your Bentley manual (if you don't have
one, you should get one!) and look into these items. You may get lucky and
just need to clean/reseat connectors or replace a vacuum line to fix the
problem, or you may need to replace the ISU or ISV.

Good Luck!

Tim

Tim

At 03:05 PM 1/4/2004 -0800, you wrote:
>Thanks to all of you who responded (both on or off list) about my new
>engine/rebuild questions.   After fixing a bizarre problem (loose
>throttle body -- see other email), I'm back to square one with
>regards to my evaluation.
>
>The situation:  85 westy automatic, 150k miles, automatic, CA emissions.
>
>- When warm, low oil pressure light comes on under 1100rpm.  I'm
>running 20w50 with a good filter and it has already had the 0.3bar
>switch mod.
>
>- When cold or warm, has rough idle, with lots of little backfires
>(pop).  If  you give it the slightest bit of throttle, the idle
>smoothes out.  Mechanic thinks the lifters are not lifting due to low
>oil pressure at idle, causing the rough idle.
>
>- Runs fine on the freeway -- I can cruise at 70, get about 17mpg,
>and it passed emissions last year.
>
>- Mechanic said "quite a bit of" metal in the oil at last oil change.
>
>The question:  Do I need a new engine, and if so, how soon?
>
>Since I'm not terribly impressed with my mechanic's diagnostic skills
>at this point, are there any other things that could be causing a
>rough idle with backfires at idle?