I checked the terminals of the throttle position sensor on my 1988 Volvo 745, only to find that 5.0 volts was being provided on pins 1 and 3, with no voltage from pin 2. As I understand, the tps on the volvo 240 that you made a video of, only provided one pin with 5.0 volts. What may I conclude?

All vacuum hoses hooked up with no leaks; all accessories turned off. New IAC and a clean throttle and TPS. The following conditions apply: (1) both IAC and TPS plugged in - idle 3200 rpm,. (2) IAC unplugged - idle either 2000, dropping to about 1100, car runs OK or idle drops off to 500 or so and then engine stalls, (3) both IAC and TPS unplugged - car takes priming to start, but runs very well. I get about 17 mpg.

There is no click when I open and close the throttle manually. Therefore, I checked the terminals of the throttle position sensor on my 1988 Volvo 745, only to find that 5.0 volts was being provided on pins 1 and 3, with no voltage from pin 2. As I understand, the TPS should have only pin with 5.0 volts, one ground pin with about 0.1 volts, and a signal pin with zero volts.
What may I be my best conclusion? I appreciate your help greatly.

 

the throttle position SWITCH is just an on-off switch, its closed ('on') when the throttle is at the fully idle position, and open as soon as you touch the gas pedal and crack open the throttle.

the TPS serves one purpose, it tells the fuel injection system to regulate idle speed via the idle air controller.

 

I replaced the TPS. Now the IAC and TPS are new. Plugged both in, hoses all attached and not leaking. Starting the car resulted in a good start, idle climbing to around 1500, dropping down to about 1000, then rising to about 2500. I am going crazy. Is there something else that I need to do?

As always, I appreciate your help.

 

only thing I can think of that would make the idle that high would be A) the throttle isn't completely closing, or B) there's a crack or air leak somewhere between the MAF and the intake manifold to head junction, or C) someone completely messed with the throttle settings.

see this for more specifics to setting up idle on a pre-1989 740 ...
https://www.volvoclub.org.uk/faq/Eng...TPSandBaseIdle

 

Thank you so much.