Throttle Position sensor on m20

[nunezfrancisco30]

How do you guys test these bad boys out?!

[EatsHondas]

How do you guys test these bad boys out?!

"Test the switch by checking for continuity at the connector terminals on the switch. Connect an ohmmeter between terminals 2 and 18. Open the throttle part way by hand. Slowly let the throttle return to its idle stop. There should be continuity (0 ohms) at the terminals when the throttle lever is approximately 0.20 to 0.60 mm (.008 to .024 in.) from its stop. Connect an ohmmeter between terminals 3 and 18. Open the throttle slowly. There should be continuity when the throttle switch is within 10 ± 2° of the full-throttle position." - Bentley

[nunezfrancisco30]

Ok I performed those steps and at no moment was it close to 0 ohms. It displayed 25.25-27.20 instead when it was close to closing. does that mean that its faulty?

[EatsHondas]

Ok I performed those steps and at no moment was it close to 0 ohms. It displayed 25.25-27.20 instead when it was close to closing. does that mean that its faulty?

Switch your multimeter to read continuity ("beep mode"), not resistance. There should be continuity between the left pin and the center pin and between the right and center pin, just at different throttle positions. As long as you get continuity almost immediately after opening the throttle with one pin and continuity as you open it to between ~3/4 and full throttle, the switch is adjusted correctly and functioning as it should.

[tomstin]

Hope someone can help me figure this out. Chasing a high idle on my new to me 85 325e. Idle control valve seems to be working, temp sensors seem good. Thought I pinned it down to the throttle position sensor. Continuity between 18 and 3 and nothing between 18 and 2. Also, oil in the intake basically filled the switch. Bingo! Got to be it! Ordered a new switch directly from BMW. Have the new switch in front of me on the bench and guess what? Same thing! Can two of them be bad? Brand new one bad? I guess maybe, but I think I'm missing something!

5 volts is present on the plug for pin 18.

[packratbimmer]

Have you eliminated vacuum leaks?

[long tall eta]

same issue with my 86 eta. replacing thermostat housing sensors tomorrow, tps and icv are good, and no vacuum leaks. maybe it's the airflow meter. i'll be following this thread.

[tomstin]

Have the new switch in front of me on the bench and guess what? Same thing! Can two of them be bad? Brand new one bad? I guess maybe, but I think I'm missing something!.

I did the red-neck smoke test and no leaks.

When I installed the throttle position switch (and throttle body gasket) on the car I have continuity between pin 18 and 2 when the throttle is closed and 18 and 3 at wide open. Car starts and idles around 1200 but sounds much smoother. As it warms up, and the thermostat opens, it starts hunting for the right idle speed. Sounds like it wants to drop down but jumps to 1800 and goes back and forth.

I start poking around and find the O2 sensor unplugged. When I plug the O2 sensor in, no change to the idle but I now have a check light on the dash and the oil light lit on the roof panel. Very strange...

I guess a O2 sensor is next on the list.

[tomstin]

Replaced the O2 sensor today, what bear getting that out. Had to run to AutoZone and get a thread chaser to clean up the threads. No check - oil light now but the idle still hunts once the thermostat opens.

Starts easy, idles real smooth at 1200 rpm and sounds good, but once the thermostat opens it starts hunting again. All three temp sensors have now been replaced. Also swapped in another Idle control box that the previous owner supplied...no change.

Beginning to think it's the idle control valve but it seems to pass all the tests I have found online. Man this is frustrating.

[tomstin]

Out of ideas, I tried the penny test with 1/4 inch hole in the intake of the ICV. Idles at 700ish even after the thermostat opens. Ordered a ICV last night. Hope that's it. If so, on to rust repair on the floor boards.

[tomstin]

New Idle Control valve and all is well. So, in the end, I was fighting multiple problems, similar symptoms and with each new part, things got better.