Making the throttle reliable...and how quickly can you kill a TPS?

[OldRanger]

Hi folks,
I have a 2005 with about 170k miles on it. I'm converting it over to a track car for HPDE, so it's under stress routinely and I need it to be reliable. Given that these events are costly, I'm trying to address the typical causes of downtime before I go to the track. One cause is the drive-by-wire throttle that consists of numerous moving parts and sensors.

1. The accelerator pedal, part number 35426786282; not available until mid-late summer 2024 and there are none of the latest part versions available used (as of May 2024)
2. The TPS Sensors, part number 13637840383; there are two and these are readily available aftermarket
3. The throttle actuator, part number 13627840537; this comes with a TPS sensor, and is available aftermarket
4. the throttle actuator pull rod, part nuber 13547839073, and is available aftermarket

There are numerous stories of EML codes, limping home, and codes 76, 78, E6, etc., and I'm one of the lucky folks that has an unexpected and joyful opportunity to sort this out. I have a few questions for the group:

1. How quickly have you killed the front TPS by the oil filter housing?
2. Have any of you ever replaced a failing throttle actuator?
3. Does the pull rod last (essentially) forever, or should it be replaced on high mileage cars?

My answers would be as follows:

1. I believe it's possible that my top side TPS has failed in two years, 18k miles, and 20 track days
2. No, but I wonder how long it can last
3. I doubt a linkage that's not lubricated could last forever; mine is original

[heinzboehmer]

I had the TPS under the intake fail in 5-10k mi. Can't recall how many track days in that time frame, but there was definitely track use.

Originally replaced it with one of the VNE sensors, but decided to go genuine BMW the second time around. Time will tell if there's any difference in quality.

Also, looks like the E46, E39, E38 and E53 all use the same throttle pedal. Might be worth ripping one out of a junkyard car to test with (or a couple to rule out a bad junkyard pedal) if you think that's the culprit.

[OldRanger]

I had the TPS under the intake fail in 5-10k mi. Can't recall how many track days in that time frame, but there was definitely track use.

I just replaced the TPS by the oil filter (VNE, with BMW markings ground off) with a new VNE as an experiment. The white plastic in the one I removed was slightly discolored and the screws should have been a bit tighter.

Also, looks like the E46, E39, E38 and E53 all use the same throttle pedal. Might be worth ripping one out of a junkyard car to test with (or a couple to rule out a bad junkyard pedal) if you think that's the culprit.

That's an idea worth considering - I do have a spare accelerator pedal of the older part number.

I also want to test the TSP and the pedal, but I don't have the proper test equipment.

[PetrolM3]

I had all 3 sensors fail under 100k miles in this order: front by oil filter housing, rear on actuator, and accelerator pedal. I first replaced the front with VNE which failed within 10k. Got a second one under warranty which was defective right out of the box. Replaced with genuine BMW and solved the issue. Shortly after that, the rear one failed and I replaced it with genuine BMW. Not long after that, the pedal failed. Replaced with genuine BMW. All 3 worked flawlessly another 7-8 years though not a lot of miles (around 40K).

When I say failed - from what I remember, the sensors were so bad the car was going into limp mode. The pedal itself was choppy - the car would not accelerate smoothly... first hesitate then lurch forward.

I never had any issues with the throttle actuator or linkage.

PS. This was all street use but all summer driving and high temperature climate.

[terra]

When I daily drove the car I'd basically kill the front one on an annual basis. I just kept a spare with me at a certain point. Never had throttle pedal issues.

I had thoughts of rigging up a hall effect type sensor for better reliability, but never really got around to it.

[lemoose]

What am I doing wrong if none of these sensors have failed on me in over 100k miles? lol

[PetrolM3]

What am I doing wrong if none of these sensors have failed on me in over 100k miles? lol

Maybe they were already replaced? Mild climate? Non aggressive driving? Luck????

[lemoose]

Maybe they were already replaced? Mild climate? Non aggressive driving? Luck????

Perhaps they were replaced before my ownership- but I live in TX and it is exceptionally hot here, and I flog the car on a daily basis.

[PetrolM3]

Perhaps they were replaced before my ownership- but I live in TX and it is exceptionally hot here, and I flog the car on a daily basis.

Then either you are very lucky or they were replaced in the past. I recently sold my M3 with just over 100K miles with all 3 units replaced. The new owner is a collector and has many cars, so he may not drive it enough to experience any failures and may also some day wonder how he's so lucky that he hasn't experienced any failures.. lol

[bigjae46]

I replaced all 3 at the same time and then cleared the adaptations.

[OldRanger]

I replaced all 3 at the same time and then cleared the adaptations.

Good thinking. Did you have a new pedal, or used?

[old///MFanatic]

What am I doing wrong if none of these sensors have failed on me in over 100k miles? lol

My front sensor failed around 160k and rear around 185k. Pedal failed around 205k.
TPS sensors were replaced with VNE, no issues in years. Pedal was replaced with new current BMW.

Linkage fine and never replaced.

[OldRanger]

Another track event, another EML on the way home (Driving from West Virginia Hillfest at Snowshoe Mountain; code occurred about 1 hour after leaving venue after some miles of partial throttle behind slow traffic). Codes 76 and 78 again.

Today, I noticed that FCP Euro does not sell the VNE aftermarket BMW Throttle Position Sensor, VNE-4166000 any longer.

I ordered a Genuine BMW part so I can try the heinzboehmer approach. It would be nice to have the tools to bench test these sensors, so I could be smarter about solving the problem.

[heinzboehmer]

It would be nice to have the tools to bench test these sensors, so I could be smarter about solving the problem.

They're basically just a potentiometer, so a regular multimeter would work to bench test them.

However, the hard part would be getting the ambient conditions correct so you can replicate the failure mode. I've had success putting parts in the oven when trying to reproduce a thermal related electrical failure, but it's far from an exact science.

[Stilt]

Another track event, another EML on the way home (Driving from West Virginia Hillfest at Snowshoe Mountain; code occurred about 1 hour after leaving venue after some miles of partial throttle behind slow traffic). Codes 76 and 78 again.

Today, I noticed that FCP Euro does not sell the VNE aftermarket BMW Throttle Position Sensor, VNE-4166000 any longer.

I ordered a Genuine BMW part so I can try the heinzboehmer approach. It would be nice to have the tools to bench test these sensors, so I could be smarter about solving the problem.

You should be able to test the sensors with just a multimeter. If you rotate the sensors and have the multimeter's leads touching the sensor, you can see if the sensor outputs the correct volts. You could get fancier and get a female connector for the sensors. Then, solder wires to the pins of the female connector (so you are essentially making a bench testing harness), then use gator clips so you don't have to hold the multimeter leads on the sensor directly.

https://drive.google.com/file/d/1C4VmUVGRwu54eh-nuhFQdXwNxDBF_WCz/view?usp=sharing