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

[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.

[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)?

[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.

[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.

[old///MFanatic]

You can remove the kickdown pretty easily.

Yep

[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]

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.

[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?

[OldRanger]

Well, I’m back at it. August 2024 seems like yesterday.

Bummed and tired from a multitude of reasons, I left Summit Point Day 1 after an EML on lap 1 of session 2. The car ran the 2025 season and 5k+ odd miles clean. Now code 76 has returned with 6B (Electric throttle self test)

Friends piled in to help, and we fixed 6B with some WD40. But code 76 returned under warm/heat-soak/light-load conditions. A shop-grade scan tool seemed to point to TPS (or wire/connector)

I didn’t fire up INPA, nor did I reflash the Epic Motorsports tune. I was discouraged, and didn’t attempt any other sessio sessions.

Has anyone had to change the connectors out?

Or, do these sensors really only last a season of track use?

[samthejam]

So I fixed a car recently that bounced around some shops.

The owner, replaced the TPS sensor connector at oil filter housing. It fell apart. I didn't physically see it myself but that connector failed and it is frequently touched with oil changes right. So anything there could be suspect and should be investigated if your issue is intermittent.

He replaced it but had the wires backwards for reference and the potentiometer voltage.
It took me about 6 hours to figure out this simple mistake. I had a bunch of known good parts to test it. However INPA doesn't let you look at live TPS values of the various things in the system, which made it hard to diag.

Conditions were self test failed, and a complaint about deviation almost immediately. Which makes sense because it was seeing one at WOT and one at idle since the wire was backwards on one.

The actuator on key on looks like it compares the actuator tps to the rail tps with the self test.

You can test the actuator by going WOT, on key on it should for a second command throttle no matter what.

I think maybe zooming out mechanically here might be useful.

So there is shit that can wear out in the linkage the balljoints that drive everything. Is it possible that when these wear enough you can get EML codes?


13547839073 qt 1: main throttle rod from actuator to ITBs
13547832148 qt6: Actuates the 6 ITBs

(I carry these as spares on roadtrips)

I remember post diag, I had these questions that I couldn't find the answers too.

How do I view the raw TPS values of the pedal (two in there), front tps, and actuator tps?

How do I know my system is mechanically setup correctly? Every itb has an adjustment and 13547839073 has an adjustment.

What is an allowable mechanical deviation for worn items? These are plastic so they must wear and let's be honest who the hell lubricates the ITB system or maintains it.

[samthejam]

citing bigjae46 to show, that these bits can wear out. I just don't know if it can wear out enough to throw a CEL.

Untitled by Sam DaJam, on Flickr
Untitled by Sam DaJam, on Flickr
Untitled by Sam DaJam, on Flickr

[OldRanger]

samthejam Thanks for adding input.

I agree, and I would personally advocate for replacing the plastic parts. I replaced the six Throttle Body Pull Rods and the one Throttle Actuator Pull Rod in August of 2024. I haven't performed any mechanical adjustment procedures - does anyone have the TIS instructions for those (that they can share)?

Oh, edit, I think I understand your post now "Conditions were self test failed, and a complaint about deviation almost immediately." Yes, I had that combination of codes last weekend - first track weekend after car sitting. On the Foxwell the codes were 6B (Electric throttle: self-test) and 76 (Electric throttle: signal, potentiometer, throttle). I also once had code 50 (Switch chain, frictional connection).

I would also advocate for lubricating the throttle bearings and the coil springs (on a track car that you're routinely inspecting). In the past, my research indicated the official word was do NOT lubricate these parts. In reality - a knowledgeable, BMW-specific, trusted shop owner shook his head at that. Mine was squeaking during the Ignitiion position 2 self test.

[samthejam]

samthejam Thanks for adding input.

I agree, and I would personally advocate for replacing the plastic parts. I replaced the six Throttle Body Pull Rods and the one Throttle Actuator Pull Rod in August of 2024. I haven't performed any mechanical adjustment procedures - does anyone have the TIS instructions for those (that they can share)?

Not the TIS but this is something I have bookmarked.

https://youtu.be/3wlTF2jcS40?t=1741

https://youtu.be/3wlTF2jcS40?t=1846