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Re: Fuel Injection Control Unit Diagnostics

At 01:56 PM 2/26/98 -0500, you wrote:
>I have been tracing down a high idle in my 88 90Q. From pulling out the
>codes, I got 4431 (ISV) and 2123 (Full throttle switch). However a separate
>test of the ISV reveals that it works. The switch on the other hand, seems
>to be stuck in the open position (I checked the switch and it works). All I 
>have left to check is a possible faulty FI control unit. Has somebody 
>performed a test of this unit before? Any recommendations and an estimate 
>of how big the hole in my wallet will be if I have to replace it? TIA,

A defective full throttle/idle switch can definitely cause idle problems.
I can't tell from your note if it works or not (you said "it seems to be
stuck in the open position" and then "I checked the switch and it works").
Idle/full throttle switch on a 90q is part nbr#026-133-093-D, about US$90
from Linda.

BTW, 'working' on an ISV can be a relative term....it can be sticky
intermittently.  It's worth a good cleaning even though it tests out good.

The other good candidate is a vacuum leak in one of the two hoses leading
to the ISV.  I've got part #'s for those also if you need

Steve Manning:  stephenm@ix.netcom.com
...Physical home: Metro D.C. area, USA
.....Virtual home:  http://www.stationwagon.com