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


The Rotary Engine News Letter. Powered by Linux.
ACRE NL web site. http://www.rotaryeng.net
You Tube http://tinyurl.com/beqqxas
Copyright 1998-2013 All world wide rights reserved.