How do throttle position sensors go bad?

[slomove]

Over the last year or two my car started idling a bit erratic, sometimes good, sometimes rough and the entire low throttle range became a bit lean, as shown by the wideband lambda probe. I checked everything, nothing has changed, coolant and air temperature sensors work as well as the baro sensor. I even replace the lambda probe to be sure.

 

Now, I checked the TPS and it appears the low end is a little bit uneven in response on the multimeter but what really surprised me that I measured 2 kOhms across the supply terminals. I could have sworn that it had a nominal resistance of 5 kOhm.

 

Not sure what TPS I have, it came with the Jenvey TBs from MSI. Might be Colvern or maybe not. Anyway, did somebody ever notice a wholesale resistance change on a TPS? I have a hard time to believe that can happen. But in any case I guess I should replace it.

 

This is for a ZX1 with Jenveys and Emerald M3D ECU.

[jlumba81]

Heat, age and vibrations usually kill electrical components. My 7 has a high ,2000 rpm, cold start idle, but goes down after its warmed up.

[speedwagon]

throttle position sensors are variable resistors, and will increase in resistance with heat, and some of the change can be permanent, the hotter the more so. a heat shield or heat sink where attached will help as will anything done to keep engine room cooler.

[bsimon]

Jenvey kits usually come with the notorious Colvern TPS. Complete crap. Been through 2 Colvern pots since I installed FI.

 

I switched to a TPS off of a BMW 328. It required machining up an acetal spacer and shaft adaptor of stainless steel. You'll need a 3 pin AMP junior timer connector to complete the swap. The 328 TPS can be had in most Pep boys stores, although they are cheaper from Rock Auto. I don't have access to the PN at the moment, but I can post it here Monday.

 

http://usa7s.com/vb/attachment.php?attachmentid=5182&stc=1&d=1373769922

[slomove]

For now I mounted a TWM position sensor that I still had as a spare. But it looks like the difference screwed up my map enough that I have to do some work here, even after recalibrating the sensor.

 

I also found that Jenvey now offers a customized non-contact hall effect sensor from Penny&Giles that fits directly onto their throttle bodies. Costs a whopping 96 GBP plus shipping but I ordered it anyway. That should hopefully solve the reliability problem.

 

All that crap 2 weeks before I want to go on that long trip to Canada.

[bsimon]

Better to sort this out in Sunny CA than in the middle of the Great White CA.