RE: E30 4 Cylinder Running Problem

[ToMoyer@xxxxxxx]

The other day, thru the Digest I wrote about a running problem with a E30
318i.  Well the problem is solved, but not with too much help from the
Bentley Service Manual,  nor the Hayes Service Manual.  The 4 cylinder
motors had/have an Idle and Full Throttle Position Switch on the rear side
of the throttle body.  In most cases, other than maybe needing adjustment
for correct idle speed and full throttle (it is a type of variable resistor
that sends info back to the ignition and fuel systems), there usually is no
problem with this switch (also known as a Throttle Switch).  Well it seems
as though the one on this car had gotten cracked some time in the past with
its previous owner, and not known by me.  When I cleaned the engine and
engine compartment, enough water seeped into the switch that when the
engine was started, it shorted out part of the variable resistor within the
switch, therefore not letting the ignition and fuel system know that the
throttle had been opened further than idle or fast idle speed.  Cost of the
part, about $50.00, but quite a few hours with a volt/ohm meter checking
lots of things.  As I said, the Bentley only briefly mentions the switch
and basically says how to adjust it for correct idle speed per throttle
opening (a resistance value) and another resistance value for wide open
throttle.  Nothing about switch failure or anything to diagnose it.  Thru a
large process of volt/ohm readings checking both ignition and fuel systems,
it came down to this part.  Just thought I would pass this info along for
other E30 318i owners, so they would know where to look if their car will
only idle and not take fuel when the throttle is opened up beyond fast idle
speed.

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