Hi all
Haven't mailed this list in ages.

My engine revs at idle started fluctuating to 2500rpm 2 weeks ago. This got
worse until it got stuck at 3000rpm a few times a day while driving, ie.
normal driving, let go pedal, engine keeps running at 3000. So I took out my
idle control unit (behind right rear taillight cluster) because I reckoned
the idle valve was being kept fully open. I had to readjust the idle screw
to keep the engine turning. I managed to drive to work but things went from
bad to worse with the van struggling to idle, cutting out after deceleration
and surging after delayed acceleration. The pipe was burning black as well,
evidence that the mixture was completely messed up and that there was too
much fuel and not enuf air (I use leaded fuel). Also, the engine would only
start a few minutes after cutting out, presumably after the excess fuel had
dried up.

What to do? Back home I slammed the drivers door and contemplated life's
choices. Not for long, though, because soon I was prodding around the engine
bay with my multi-meter checking resistor tolerances. Good news. I think the
problem was the microswitch under the throttle body. I dismantled, cleaned
and spent about an hour adjusting. The Haynes manual stipulates 1,5 ohms or
less at idle and full throttle. My reading was 0.3 ohms and after studying
the mechanism I realised that this value is *not* adjustable and merely
represents the resistance value of the microswitch when it is engaged. I
figured that, with my foot off the pedal, the microswitch was indicating
acceleration (no resistance), exciting those injectors. Since the air flap
was closed (foot off pedal), there was not enuf air, causing flooding and
cut-out.

The engine has been running beautifully now for the last 2 days. Next I plan
to replace 2 burnt resistors in the idle control unit and see what happens.

Hope this helps somebody.

Regards
Nigel
Cape Town, SA
1989 Caravelle Syncro