355 Throttle Position Sensor - adjustable??

Recently replaced my TPS as a likely fix for my car's tendency to increase idle speed substantially once warm and in neutral, as well as failure to return to idle speed when coasting / letting completely off the throttle. Fix appeared to be successful at first, idle is dead steady at all times, no more hunting. But now, when I give the car any throttle off idle it immediately hesitates and almost dies, then catches and runs ok. Car is barely driveable when cold, gets a little better once warm.Thought maybe I had a vacuum leak but have checked every single connection, all OK. No fault codes on the OBD. Put the old TPS back in to see if this was the problem, no difference. A friend who is familiar with BMW Motronic thought that there needs to be a reset of the TPS to bring it to "Zero Ohm" at rest, but the device itself screws on to the head with no adjustment slot of any kind. Does anyone know if there is some adjustment procedure to reset the TPS to Zero? If so, any copy of procedure available?

Thanks!!

Steve Berman
'97 355GTS Titanium / Black

 

all 02 sensors as well as cats are recently new, and except for the creeping idle, the car was always a screamer with no hesitaion of any kind till the replacement of the TPS, so I will assume this is the problem. Never had a fault code with the climbing idle, but a light tap on the R/H TPS when idle would start to rise to 1500 or sometimes 1800 rpm would yield an immediate return to normal, and in fact the car now idles all day long at a very steady rpm.

So assuming my problem is the sensor postition, all adjustment range is made by the almost imperceptible movement of the device in the fixed screw holes? Seems like it would have been a slotted arrangement if adjustment was carried out at that location, but I will certainly give it a try.

Thanks, will let you know how it works out tommorrow night.

 

Sometimes help comes from the strangest sources. A friend was helping me replace the dash pad on my Sunbeam Tiger, when he noticed the broken down Ferrari parked nearby. He asked me what the problem was and I gave him the rundown. He asked me if I had done any other work on the car besides changing the TPS, and I mentioned I had done an oil service and replaced the Air Filters, and while the plumbing was apart I cleaned all the air ducting inside as well as the Mass Air Flow Sensor with a q-tip and some rubbing alcohol. Turns out before turning his talents to ancient Lucas equipped Sunbeam's, he worked exclusively on late model BMW's with 5.2 Motronic, and he bet me that I had ruined the MAF sensor by cleaning it, even gently. He also suggested I purchase a 97 or 98 BMW 540i unit, which is identical, at a fraction of the cost from Ferrari, which I did.

Plugged the new sensor in and he was 100% correct! The car runs perfect. Lesson learned and passed on to all, NEVER attempt to clean the sensors on your MAF, no matter how gently, as it will become toast on contact!

 

The sensor appears to be identical on the '97 '98 540i, I think the later models use a different version. You can go to Rock Auto online and search the 97 540i Sensor, they give you the oem Bosch part #, then take a look at the '97 355 Sensor, same exact #. I get a discount at my local BMW dealer so it was cheaper for me to buy one from them, but either way much cheaper than going to your Ferrari dealer. Almost all of the Motronic parts are available cheaper from the "more conventional" auto manufacturers, we just need to compile the part numbers into a master cross reference and start saving some $$!