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

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