Throttle Position Sensor voltage out of range

[Jamie Reid]

When reading your voltage, on the TPS, put your black meter lead on the black/white instead of a convenient ground. The black/white is the true ground for the 5v supply. While it should be close to the same, if it isn't, that may be a clue.

This is how I have been testing

 

[Jamie Reid]

your vacuum gage should give you some indication of things to though.

at idle, what were you reading on it? you can use it to set your timing too, if you need to do that. it actually is good for a fair number of things. google the chart that shows all the readings the vacuum gage gives so you know what you are getting from it

I’ll have to purchase one

 

[RonD]

Highest voltage in a vehicle with engine off is 13.0volts, new battery voltage, after a few months its lower
12.3v to 12.8v is expected as highest battery voltage engine off

So 14v wouldn't be possible unless engine was running, alternator makes 13.5v to 14.8v, and you wouldn't test TPS with engine running, just key on
So I would say you have a glitch in the meter or test method

Yes, you can test upper and lower wires on TPS to see if you get 4.9v to 5.1v from computers 5v power supply
And use that ground to test center wire
Wire colors change over the years

 

[franklin2]

Wire colors change over the years

This is worse that you would think. Most white wires are yellow now, and the ones with white stripes look like yellow stripes. Blue wires take on a greenish tint. The heat from the engine over the years really deteriorates things.

 

[Jamie Reid]

I ended up splicing out t

If vehicle has AC make sure its turned OFF for all the following

1988 2.3l has a distributor, so first thing you need to do is set the base spark timing
Warm engine, SPOUT connector unplugged

Adjust the Anti-diesel screw next, its not an idle screw since fuel injected engines can't have/use an idle screw, lol
Warmed up engine
Let it idle, SPOUT plugged back in
Unplug the 2 wire connector on IAC Valve, idle should drop to about 600-650RPM on a 2.3l
If engine stalls turn screw clockwise a full turn, and restart engine
Set screw so engine is barely idling, about 650RPM
Its now set

Plug back in IAC valve and RPMs should go up to 750 to 850 depending on manual or automatic transmission
If idle didn't drop when IAC Valve was unplugged then you have a vacuum leak

Engine OFF, warm or cold doesn't matter, key on
Use a sewing needle/pin to test center wire on TPS
Throttle close should be 0.69 to 0.99volt, 0.98v is fine
Open throttle slowly and voltage should go up smoothly and be at 4.5-4.7volt at wide open(WOT)
Adjust TPS for these voltages

Yes, TPS is a 5volt sensor, all sensors are 5volt, just FYI
TPS is there to prevent engine from stumbling when accelerating and to turn OFF injectors when coasting
MAP or MAF air sensors can't respond fast enough to higher air flow, computer needs instant information so it can add more fuel as soon as gas pedal is pressed or engine would stumble
TPS does what Accelerator pump did in a Carburetor, instant fuel added

ECT(engine coolant temp) sensor is 5volt, and computer uses it on start up to set Choke level
So odd startup issues that clear up after a minute or so can be failing ECT sensor
Its reporting extreme cold or hot temp with key on, so computer is using the wrong fuel mix at startup, warm or cold

Just FYI, Coolant temp SENDER is 12volts and only used for dash board gauge
ECT sensor is only used by computer

i did these steps in this order and it helped out quite a bit. I was 10 degrees out on my timing. I got the tps adjusted to the right range and I appreciate the information very much. Unfortunately the ect is still giving me a fit, but at least I am getting closer