The TPS is the Throttle Posistion Sensor. If it's bad it may cause your
ECM to think that you are moving the throttle. The
ECM then tries to increase or decrease the fuel flow
to match the (improper) throttle posistion. You could also have a bad
IAC (Idle Air Controller) or bad
EGR valve.
You can check the TPS by disconnecting the electrical plug on the TPS unit.
The ECM will now use a default value. If your idle
problems disappears then replace the TPS unit. BTW, the car may be hard to
start and _will_ be down on power with the unit disconnected.
From: Lee Brown
The code 22 is set if the voltage from the TPS is less than 0.2 volts for
more than 2 seconds while the engine is running. Check the voltage on the
wire connected to the wiper terminal of the TPS. It should vary from a few
hundreds of millivolts to a little below 5 volts depending on the throttle
position, and do this smoothly without bouncing the needle around (if you
are checking it with an analog voltmeter).
The problem probably is in the TPS, but check also for a short in the TPS
signal wire to ground.
From: Jukka Alve
4 Cylinder Models
I don't have an '87 Fiero manual available to me, but I believe the color
codes I'm about to give you should apply for '87. Check your TPS connector
to see if it matches the following:
Pin "A"- Grey wire, 5v reference from ECM
Pin "B"- Black wire, Sensor ground from ECM
Pin "C"- Dk. Blue wire, TPS output to ECM
If your TPS matches these color codes, then you would measure pin "C" as
described in previous responses (ignition on, engine off, sensor connected,
around 0-5v range from sensor, smooth voltage measurements as throttle is
adjusted). With the TPS disconnected, if pin "A" of the harness connector is
not providing around 5v, or pin "B" is not near 0v, then you may need to
check the ECM or wiring.
If the pins and colors don't match this indexing, then you'll likely find the
Dk. Blue wire in pin "B" and the Black wire in pin "C". Either way, you want
to measure the voltage output at the Dk. Blue wire.
From: Bret Scott
The TPS really isn't difficult, IF you take the
EGR valve off first. The
EGR valve is just attached with a couple of
bolts. There is a gasket between the EGR valve
and manifold, so you might want to get one of those (Auto Zone stocks them).
The TPS on my son's '84 was attached with Torx
fasteners. After disconnecting the electrical connector, just undo the
Torx screws. I used a set of
Torx
I also bought the new TPS at Auto Zone. It was in a Wells box, but is an AC
part!! Once you put it on, you have to identify which contacts in the plug
have voltage, and then do some jumpering between the TPS and wiring harness.
Then there is a calibration to go through, which is just rotating the TPS to
achieve the desired voltage with the throttle closed. This also is not
difficult, but you definitely need the digital volt meter, and some jumper
wires. There are instructions with the TPS.
The new TPS came with new screws, but they were Phillips. I thought the
Torx was better, so I reused them. But one broke on
installation--the head snapped off. Perhaps that's their safety to prevent
overtightening! By the way, if you haven't already done it, you might want
to replace the vacuum line to the EGR valve.
From: Earl Zwickey
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