When turning ignition on, I get a rock steady reading with my voltage meter of the TPS at 0.32-.34V. (measuring yellow/red wires)
But when idling, the voltage readings are all over the place on my digital meter, and my idle slightly stumbles (in other thread). Shouldn’t the reading also be rock steady when the engine is idling?
What would cause this?
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
2
Yes. That fluctuation might be a sign of a shot TPS, but it also might be a sign of a flaky connection somewhere.
Meter the voltage to the TPS while idling. Yellow and Green On the TPS side of the connector. If thats a steady 5v then it’s the TPS.
The YB ground and YK positive supply wires for the TPS also spur off to feed the CTS (YB) and ATS (YK) if that supply voltage is flakey then it would affect all three ECU inputs.
With engine idling, intermittently voltage will jump around (flashing diff numbers between 5v and 16v) and then come back to 4.95V. Sometimes will go a good 10 secs before voltage jumps around.
I tested this with both yellow/green and green/ground.
No, I don’t think it can short, it just looses contact. I would take the TPS apart to check it’s condition and see from there.
I added a small washer inside mine because it was doing exactly that.
Been watching a lot of You Tube. Some really smart guys fixing a lot f different things. some blabber a bit, but, oh well!! Makes it more interesting than a strict tutorial.
J.C. Smith. Deals in old trucks. Buys what are usually older Fleet vehicles, From pickup to semi’s… A lot of diesel, but some gas.
A Ford V10 with engine issues. Broke it down.
A toothed wheel with a gap. TPS Ford style. the GAP tells the PCM, TDC!!!
As an OHC engine, a very long chain. Tensioner and guide ala Jaguar!! I wonder?? Oil Pressure applies the pressure and takes up the slack. If they leak, the engine clatters at start up for a moment til pressure.
More on point
A. Where did 14 v come from? Flaky alternator.
B. Does odd voltage matter, so long as the PCM aka ECU. gets the signal.
Or so sophisticated that variations in volts depict crank location in degrees?
C. Where in he harness does the TPS get it’s volts.