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

[ac427]

78 [120] EDK: potentiometer, signal comparison
78 [120] EDK: potentiometer, signal comparison
PaSoft.
At least for me these were the codes and can confirm it was my pedal and not my TPSs.

The EDK values can be viewed in INPA.

Do the separate TPS values also appear in INPA?

[old///MFanatic]

Thanks for that information. What is the code for a bad pedal (and what software/device)?

78 [120] EDK: potentiometer, signal comparison
78 [120] EDK: potentiometer, signal comparison
PaSoft.
At least for me these were the codes and can confirm it was my pedal and not my TPSs.

[OldRanger]

Another EML yesterday. I’m done with this… I’m going to throw parts at it.

I really don’t understand this problem if it’s simply the throttle position sensors. They shouldn’t fail in just a few thousand miles - even with track time.

Today I installed a new throttle actuator (with new TPS), a new pull rod, and new Genuine BMW TPS up front. I know, I’m just throwing parts at it…but I have 172K miles. So, if my assumption that a new throttle actuator is manufactured at the same quality as the OEM parts, then in theory I’m just replacing things that would likely wear out over time and use.

Other concerns: I’d also like to add that there’s a fair amount of front to back play on the throttle operating rod. This shouldn’t be an issue, but I wanted to mention it. Ther is also slop on the short plastic pull rods (x6) for each throttle body. Maybe I should replace them…even though the original main pull rod didn’t seem noticeably different from a new one.

[old///MFanatic]

You can remove the kickdown pretty easily.

Yep

[Slideways]

I keep a spare TPS in the car. They're light weight, responsible for... 40% of issues on the car? And swapping them out takes either 2 min (front) or an hours (under intake).

The actuator and arm seems pretty reliable-- I'm willing to roll the dice on those. In 20 years/300,000 s54 miles, never had an issue with one of those (unlike the S85, where I've had failure).

The pedal you could replace once and carry the original as a spare in your track kit. They do fail, but not like the TPSs. Automatic/SMG cars have a kickdown switch that I find annoying, so if junk hard driving a part, avoid that. There is a mount under it that sometimes gets brittle and fails, so maybe grab a spare that if you're carrying a spare pedal.

You can remove the kickdown pretty easily.

[Obioban]

I keep a spare TPS in the car. They're light weight, responsible for... 40% of issues on the car? And swapping them out takes either 2 min (front) or an hours (under intake).

The actuator and arm seems pretty reliable-- I'm willing to roll the dice on those. In 20 years/300,000 s54 miles, never had an issue with one of those (unlike the S85, where I've had failure).

The pedal you could replace once and carry the original as a spare in your track kit. They do fail, but not like the TPSs. Automatic/SMG cars have a kickdown switch that I find annoying, so if junk yard driving a part, avoid that. There is a mount under it that sometimes gets brittle and fails, so maybe grab a spare that if you're carrying a spare pedal.

[OldRanger]

My bad pedal absolutely put my car into limp mode. It also throws a code pointing to the pedal.

Thanks for that information. What is the code for a bad pedal (and what software/device)?

[old///MFanatic]

As far as I know Hella is the T1 supplier for these parts.
I have replaced the front unit twice with aftermarket and failed within 5k kilometers. Last time I used Hella and no issue since 30k kilometers.

I’d have to look at stock TPS to see who makes it. So if you’re saying Hella makes them for BMW that’s possible. For the record VNE is just a supplier of OE parts they buy. They don’t make stuff. They scratch off the BMW logo and sell.

[old///MFanatic]

OK, I did that (Epic Motorsports reflash). I also swapped the accelerator pedal with a used one I purchased back in May when I started having unexpected issues with two new TPS sensors. I chose to swap the pedal out because: 1) The most recent EML lights didn't put the car in limp mode. 2) The symptom I could feel, seemed like the car was bucking a bit when I would shift under heaving acceleration. Almost like it didn't know how much throttle to give. Given what the documentation says, I decided I would hedge my bets on a bad pedal.

My bad pedal absolutely put my car into limp mode. It also throws a code pointing to the pedal. You can just reset the pedal adaptations turning key On and holding pedal down. This can help with diagnosing and getting temporary out of limp mode.

[OldRanger]

No EML today. Not at the track, nor on the way home.

[Ryan_R]

If you want to try to nuclear overkill approach, there is always this option.

[ac427]

Update: I don't think bench testing resistance (kOhms) is going to give reliable results.
Justification:

1. Even two, brand new sensors produce different values at 'full' counter-clockwise and 'full' clockwise.
2. The part of the sensor that rotates can wiggle or jostle in the sensor body, even at the stop positions and produce minor differences in the reading.

Stilt has provided the BMW tech manual description of how these work. That hasn't led me to a better testing approach. I suppose BMW Dealerships have sensor test equipment that can simulate throttle input to test the TPS sensors. The manual did help clarify the function of the pedal hall sensors. These are critical, because no one wants the lesser value.

Just as bigjae46 mentions...replacing them all would likely solve the problem, but there isn't a source for new pedals that I'm aware of. I have a spare used one, I suppose I can experiment with that one.

Testing the TPS sensors on an analogue multimeter may help in seeing any deviation from a sweep of the wiper.

[OldRanger]

I'd first try reflashing the ECU.

OK, I did that (Epic Motorsports reflash). I also swapped the accelerator pedal with a used one I purchased back in May when I started having unexpected issues with two new TPS sensors. I chose to swap the pedal out because: 1) The most recent EML lights didn't put the car in limp mode. 2) The symptom I could feel, seemed like the car was bucking a bit when I would shift under heaving acceleration. Almost like it didn't know how much throttle to give. Given what the documentation says, I decided I would hedge my bets on a bad pedal.

My test drive included some WOT pulls and partial throttle shifting. No EML (knock on wood).

If I get another EML at the track I'm going to install the new throttle actuator and actuator arm that I have, and a new BMW TPS on the top/front position.

[bigjae46]

Update: I don't think bench testing resistance (kOhms) is going to give reliable results.
Justification:

1. Even two, brand new sensors produce different values at 'full' counter-clockwise and 'full' clockwise.
2. The part of the sensor that rotates can wiggle or jostle in the sensor body, even at the stop positions and produce minor differences in the reading.

Stilt has provided the BMW tech manual description of how these work. That hasn't led me to a better testing approach. I suppose BMW Dealerships have sensor test equipment that can simulate throttle input to test the TPS sensors. The manual did help clarify the function of the pedal hall sensors. These are critical, because no one wants the lesser value.

Just as bigjae46 mentions...replacing them all would likely solve the problem, but there isn't a source for new pedals that I'm aware of. I have a spare used one, I suppose I can experiment with that one.

I'd first try reflashing the ECU.

[OldRanger]

Update: I don't think bench testing resistance (kOhms) is going to give reliable results.
Justification:

1. Even two, brand new sensors produce different values at 'full' counter-clockwise and 'full' clockwise.
2. The part of the sensor that rotates can wiggle or jostle in the sensor body, even at the stop positions and produce minor differences in the reading.

Stilt has provided the BMW tech manual description of how these work. That hasn't led me to a better testing approach. I suppose BMW Dealerships have sensor test equipment that can simulate throttle input to test the TPS sensors. The manual did help clarify the function of the pedal hall sensors. These are critical, because no one wants the lesser value.

Just as bigjae46 mentions...replacing them all would likely solve the problem, but there isn't a source for new pedals that I'm aware of. I have a spare used one, I suppose I can experiment with that one.