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Hello, We have 1996 ford f350 5.8 with constant high idling at 1500 rpm. Replaced iac tps was replaced a couple years ago.
.Tps voltage koeo .085 power 11.74 ground 0.92 signal. Throttle stop screw has been tampered with by previous owner.
There are no codes and no vacuum leaks. Any suggestions would be appreciated. Thanks.
Is your timing set to 8°btdc with the spout connector removed?
if you can get your hands on an oscilloscope, you can check your TPS sensor for open spots which can cause high idle. You can do it with a multimeter too if you open the throttle slowly while watching the voltage.
Manually rotating the throttle with multimeter no increase or decrease in voltage,
You're either probing the wrong wires or the sensor is dead. The 0.92 closed voltage you reported in the first post was good so it's hard to say what is going on from this end of the internet, are you probing wires with pins or looking at scanner data?
Assuming you are probing the correct wires then the sensor is either broken or incorrectly installed. An analog multimeter is the right tool for this job but even with a digital if the thottles are opened very slowly you should see the voltage gradually increase towards 5v at WOT.
The only picture I could find shows the TPS with the harness coming off to the rear, so the pigtail could route to the drivers or passenger side from there.
If you disconnect the sensor and probe it directly with the meter on the Ohms setting you should see the readings change as the TB is opened, if it doesn't then the sensor is not physically keyed to the pivot shaft.
The direction of the sensor should not matter, I played with this since there is conflicting information out there. As long as it is correctly keyed to the shaft it will work.
It is very difficult to install without removing the throttle body. There should be a small spacer (plastic ring) to aid alignment. With the throttle body off it is very easy to see if it moving correctly with the shaft or not.
For what it is worth the factory service manual shows the 5.0/5.8 TPS keyed with the pigtail pointed toward the passenger side. This is how my NOS throttle body was set up as well.
The only way to adjust it would be to open up the mounting holes on the sensor.
If the stop screw has been jacked with you need to set it up correctly and then recheck your TPS readings. Assuming the sensor is okay you should not need to adjust it if the throttle body is set up and working properly.
Warm up the engine. Disconnect the IAC. Idle should drop to 600/750rpm or even stall. If not adjust the stop screw to obtain an rpm in the above range without any mechanical binding. Turn engine off and reconnect the IAC.
This should put the computer back in charge of the idle via the IAC. Recheck your TPS readings. It is normal for the computer to raise the idle under various circumstances but generally sitting in gear, brake applied, no HVAC, the idle should be fairly low and stable. Typically 750rpm or less.
You can confirm the computer is happy by running KOEO and KOER tests. The KOER includes an IAC control test.
