Throttle Position Switch, 1990

[scott 4991]

I'd like a verification on the Throttle Position Switch on a 1990 535i. I have the Bentley service manual, page 130-8, upper right corner, shows the TPS as being basically 2 switches, one closed at the idle position, one closed at the full throttle position. I can measure the closed position on the idle, but can't measure it on the full throttle position - the switch shows 200+ ohms, but varies - but it's not a dead short for sure. Can someone verify that pins 4-5 on your TPS are shorted when the throttle is full open?

This TPS is about $150, so I want to be sure it's bad before I get a new one from BMA.

History: I set the TPS perfect at the low end, closed at idle (using a good ohm meter). Then at full throttle I never got the switch closed - always open. Yesterday I worked backwards, thinking maybe if I rotate (adjust) the TPS at the top end for closed, the bottom end (Idle) would take care of itself. I could get the top end at the 200+ ohms point, but not a dead short. The bottom end was close, so I left it. The car runs fine at idle, but I'm not sure I'm getting the 'boost' at the top end.

Thanks for any help.

sc

[Bill R.]

an automatic , in that case here's the procedure from bmw.http://www.bimmernut.com/%7Ebillr/images/tps%20adjust.jpg







I'd like a verification on the Throttle Position Switch on a 1990 535i. I have the Bentley service manual, page 130-8, upper right corner, shows the TPS as being basically 2 switches, one closed at the idle position, one closed at the full throttle position. I can measure the closed position on the idle, but can't measure it on the full throttle position - the switch shows 200+ ohms, but varies - but it's not a dead short for sure. Can someone verify that pins 4-5 on your TPS are shorted when the throttle is full open?

This TPS is about $150, so I want to be sure it's bad before I get a new one from BMA.

History: I set the TPS perfect at the low end, closed at idle (using a good ohm meter). Then at full throttle I never got the switch closed - always open. Yesterday I worked backwards, thinking maybe if I rotate (adjust) the TPS at the top end for closed, the bottom end (Idle) would take care of itself. I could get the top end at the 200+ ohms point, but not a dead short. The bottom end was close, so I left it. The car runs fine at idle, but I'm not sure I'm getting the 'boost' at the top end.

Thanks for any help.

sc

[scott 4991]

Thanks Bill, this is the same procedure in the Bentley book. As this is a mechanical connection, I can not see it going bad - this is why I'd like to see if someone can check theirs to make sure the resistance at full throttle goes to zero ohms. If so, mine is bad for sure. If their's goes to 100 ohms, mine is more than likely OK. I do not read near 0 ohms at full throttle.

sc

[icesoft]

I measured mine with the connector off about 2 days ago, pins 4 and 5 go to dead short at WOT, Pins 4 and 6 are shorted at closed throttle.

I'd set the switch based on closed throttle (closed throttle is more important to it will idle properly and won't die), then adjust the open throttle set screw on the linkage if it doesn't open enough to trip the WOT switch.

[scott 4991]

Thank you icesoft - I will check my WOT settinng with the screw - will be interested if this helps.. but it seems like mine is bad. I will order one tomorrow if the screw does not help.

appreciate the info.

Scott

[scott 4991]

Got the new TPS today, it works perfeft - can't believe the other one was bad, but at WOT it measured 5 ohms, and varied + 4 ohms. The new one is a dead short at about 3/4 throttle to full throttle - cool! Thanks for the info.

sc