[Shotimes] TPS Mod

[Carl Prochilo]

After reading about this mod for years, I decided to try it out for
myself.  Here are the results.  Thanks to Mark Nunnally for coaching me
through this.  I'll post a few pics of this to my website later.

Why do this at all.
By setting the TPS starting point at right under 1 volt, you don't have to
push the gas as far to break the 1 volt level, which is what the EEC-IV
senses as off idle.  More precise throttle "tip-in" will be realized
resulting in better driveability around town; a nicer, crisper throttle
"feel".

Tools needed.
Digital voltmeter.
Paper clips or stiff wire to create probe points in the TPS wiring harness
Phillips head screwdriver
Dremmel tool and/or drill with a decent selection of drill bits.
Cutting wheel for Dremmel tool
1/4" ratchet to remove Throttle Body plastic cover (if you have one)

Procedure.
I started by removing the top screw on the sensor okay, but got stopped by
the lower screw.  The phillps head screw was frozen, and in the end the
only solution was to cut the head off the screw.  I went to the local AZ
and bought a new TPS for $25, plus a die-grinder wheel for my dremmel tool
one of those oversized hardware stores.  I thought it was the threads in
the TB that had frozen, but after I cut the head off the screw using the
dremmel, I realized that the screw shaft had frozen in the the TPS casing
causing the obstruction.  This is the second frozen screw in the engine
bay I've had to hack-off.  Yes, it is an old car.

The part number of the original sensor is E9TF 9B989 BA .  AZ lists three
different part numbers for the SHO engine.  The TPS looks identical in
every way to the original except for the printed numbers.  I installed the
new TPS and it read 0.776V.  Better than the original at 0.714V, but not
nearly good enough.  I tried rotating the new sensor clockwise as far as
it would go and got into the 0.8s, but still off the mark.

Mark had mentioned that I might need to take a drill or dremmel to the
TPS, and so that turned out to be the case.  Since I was going to do this
surgery, I decided to use my original TPS as it was still working fine. 
To get enough rotation on the TPS, I needed to space past the metal collar
into the plastic housing.  I used the drill with a 1/4" bit for the gross
work, and the dremmel with a file attachment as a finishing step.  After a
lot of manipulation I was able to rotate the TPS clockwise enough and I
now get a 0.996V reading at idle.  The WOT reading is 4.61V.

The amount of hacking of the sensor is what surprised me.  I totally
underestimated the amount of work I needed to do to make this adjustment.

Other factoids:
The measured voltage at KOEO vs KOER was basically the same.
I used anti-seize compound when installing the TPS to keep the threads
from getting frozed.
I read somewhere that people adjust the idle screw to compensate for the
voltage reading.  I've been told to NOT mess with that adjustment.  With
this procedure, you're only resetting the staring point of the TPS for
where the throttle is presently set, not the actual idle setting.

Driving impressions:
I took a quick drive and it does feels a crisper.

Cheers,
Carl Prochilo
92 Ultra Red Crimson
201K+ on the odo