Hi, Paul, I have a lead on a 1991 RX-7 (non turbo) that the owner
says needs a throttle positioning sensor. It idles at about 3000 rpm.
I have called my local parts dealers and it appears that a
replacement part is from $400 to $600. List is about $900. How can I
prove to myself it is in fact a TPS problem, and if it really is, do
you or anyone else reading this, have a source that can save me any
$$? Do the race cars even use TPS's, and if not, can I get one they
might otherwise throw away? Thanks for any help you can provide.
Gerry Hanscom P.S. I'm going to be at Sun 'n Fun. Hope to see you
there, but I would like to react on this RX-7 before then. Thanks
again.

I might be at Sun N Fun. If so I plan to spend a lot of time in the
Lincoln welding tent learning how to tig weld aluminum.

TPS are simple devices. Basically just a potentiometer connected to
the throttle shaft . I suggest looking on Ebay. A unit for a
different kind of car with about the same power would work.

Paul Lamar

Paul, Thanks for the speedy reply to my query. I was hoping you would
have some thoughts about how to be sure it is the TPS causing the
high idle rpm. Is there a way to tell without having to take it to a
dealer? Thanks again. And I will look for you in the Lincoln tent at
Sun 'n Fun. Gerry Hanscom

No I don't. Could be a lot of things.

Could be a block temp sensor telling the computer the engine is cold
so the computer idles the engine faster but not 3000 RPM :)

I think the 1991 may have some built in diagnostics. Download the
shop manual from here.

http://foxed.ca/index.php?**page=rx7manual<http://foxed.ca/index.php?




page=rx7manual

Paul Lamar

Basic thought on EFI systems; each sensor except the O2 will let the
computer see a voltage between0 and 5 volts. Generally 0 volts will
not be used and the low range will be 0.7 to 1.0 volts. MORE volts =
MORE fuel. The TPS sensors are generally adjusted to provide about
0.9 volts at idle. Consult the specific manual for the exact range
for your year and engine. To test the volts you need a digital multi
meter, the manual and some T pins from a fabric shop. The T pins
work well to get between the wire seal and the wire without damaging
the seal or puncturing the wire. The pin will contact the terminal
inside the connector without removing it. The sensors usually have
three wires, but could be more. The three wires are =5volt supply,
ground and signal. It is the signal you need to read. The mounting
screws are loosened and the sensor rotated to adjust. Also as you
open the throttle you should see a steady increase in volts. On
higher mileage units they can develop an open or off resistance or
voltage where the throttle is in most common driving speeds. The
meter will drop or go high for a split second as you pass this area.
This usually causes a stumble during acceleration.

Dale Davies


Before forking over $600, it seems that it would be easy enough to
bench test the TPS if you have the specs which you should be able to
get from the manual Paul referenced.

Mark S.

Gerry, There should be a lot of used TPS sensors out
there.........Check local salvage yards, E bay, etc...........I have
bought a lot of parts from a Texas Mazda salvage called "REVVIN
SEVENS"............They are on E bay also...........

http://revvinsevens.com/home

Kelly Troyer


It is more likely to be the idle up stepper motor or plunger, as has
been said the TPS is a potentiometer sometimes with a switch at idle to
switch off things, the idle up could be wide open allowing a lot of air
to bypass the throttle plate, some Jap cars have a stepper motor which
steps the plunger in and out decreasing and increasing air flow past the
throttle plate, try removing the air cleaner hose to throttle body and
find the rather large hole where the air is sucking in around the
throttle if it is allowing heaps of air when the engine is at normal
operating temperature block it with your finger the engine may stall,
then clean around the throttle plate to ensure there is no dirt and
gunge stuck around, then restart motor allow a little air past your
finger if motor stalls with hole completly blocked. One can test the
idle control motor, I have had a Mitsubishi that would stall at the
lights, never at any other time found to be a stepper motor going open
circuit on a hot day with the bonnet (hood) closed, fitted exchange
motor no more stalling, the motor was closing off the idle passage
completly when hot.
      John Burey


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