Per the BMW E30 Factory Manual:

Per Bentley manual:

To set between 0.20mm and 0.60mm:

Failure Methods:

It is commonly stated online that E30 TPS failures are caused by oil saturation. Crankcase oil can migrate down the throttle body shaft bearings and into the TPS, leading some to recommend drilling a hole in the bottom of the TPS to allow the oil to drain.

However, TPS switches rarely fail due to engine oil. Engine oil is non-conductive and can even help by preventing internal moisture buildup.

The most common cause of TPS failure is cracks in the internal solder joints. These cracks are often small and can cause intermittent failures, as they may temporarily reconnect or disconnect due to thermal expansion.

Another factor is the wear and tear of the idle switch within the TPS, which is designed for a finite number of cycles and will eventually wear out.

Additionally, after 30+ years, the O-ring that seals the TPS to the throttle body often becomes dried out, compressed, and unable to maintain a proper seal. This leads to small vacuum leaks, as air can pass through the TPS and around the throttle body shaft bearing. Installing a new, well-sealed TPS prevents excess oil intrusion—similar to how liquid cannot be forced into a straw if one end is blocked with a finger.

Although OEM Bosch TPS’s are still available, the Made in Italy Facet TPS’s work equally well, and are internally sealed very well. Considering there is a 6+ times price difference between the two, its often worth considering the Facet unit.

This entry was posted on November 4, 2024 at 12:21 am and is filed under Interesting Stuff. You can follow any responses to this entry through the RSS 2.0 feed.