From: Wally Plumley [wplumley@bellsouth.net]
Sent: Saturday, November 24, 2001 9:19 AM
To: 928
Subject: [928] Re: More issues on '91 GT, need help! (longish)

At 10:31 PM 11/23/01, Joseph V. Maniaci wrote:

>Thanks to everyone who responded regarding my questions about the on-board
>computer lights and RDK system on the '91 GT I got a few days ago.  I've run
>into a few more problems I need to sort out.
>
>1.  This morning the car was running very badly, like on four cylinders.  It
>did sit out all day yesterday in some pretty hard rain.  I'm assuming maybe
>a wet distributor or coils, or possibly bad plug wires.  It ran a lot better
>this afternoon (though not perfect) after sitting all day (no rain).  Ideas?

First thing to check on the later cars is the ignition monitoring system. 
There is an exhaust temp sensor in each downpipe. If the exhaust temp falls 
(or, more commonly, if the sensor erroneously reports low exhaust temp) on 
one of the sensors, the ignition monitoring relay cuts the injection to 
that side of the engine to prevent overheating the cataylic converter.

Remove the carpet cover over the ECUs on the passenger kick panels, and 
find the clear plastic relay boxes mounted tot he end of the ECUs. Run the 
engine - if a red or a green LED is glowing, the ignition monitoring system 
has killed half the injectors.
Red - Right Coil - Cylinders 1-7-6-4
Green - Left Coil - Cylinders 5-8-3-2

You can sometimes loosen and rotate the exhaust sensor and temporarily cure 
the problem.

>There was a Hall sensor fault code that my mechanic read out with the
>diagnostic computer, any relation to this problem?

Not likely - this will just retard the timing slightly, costing power and 
fuel econmy.