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Discussion Starter #1
OK,
My well published TB died a slow death and I needed to know why. Symptoms included intermittent ABS and TC lights, every couple of days, it'd go nutz and start crazy idling :icon_eek:...800, 1200, 750, 1400...since it's a 5MT, it's more pronounced. I put the last month or so of my VCDS logs at the bottom of the post...

On to the pictures...

First, opening up the TB control module cover revealed nothing too outwardly surprising. Just a simple mechanism with a motor, an idler gear and the actual gear that controls the butterfly...which also has the leads that scrape the electronic tracks of the control module, letting the ECU know the location of the butterfly in the TB. Pretty standard stuff.

HOWEVER, inspecting the parts a bit more closely, I noticed that there was some significant wear on the tracks (for electronics anyway) showing some steps on the tracks that can account for the locations of the trouble that I was having....from idle to about 1500 RPM. Notice the steps worn in the tracks at the top of the photo...they are pretty visible to the naked eye:



This makes sense based on its behavior...but WHY in a closed system is this causing an issue? Especially since the steps worn in the tracks don't look TOO bad! There's got to be another answer. So, let's go deeper. Removing the motor with a torx driver, I noticed that the case of the TB where the motor lives actually makes up the stator with the perm magnets there and the commutator riding on a pressed in bushing inside the TB (notice the messy black/iron color dust inside the motor can...)



and another on the motor cap that's unscrewed (notice the color of the magnets on the commutator)...


After noticing the aforementioned rusty commutator magnets and dusty crap inside the motor can, I started to look for some more subtle issues that may have let some moisture/grit inside this thing. I found my answer after pulling up on the seal a little:



Yes, folks....moisture intrusion killed this TB. I think what happened, based on my forensic analysis is that this thing started to go bad and it was cracked open and the seal wasn't positioned properly...allowing that awesome Connecticut environment inside...killing it dead.

So, YMMV, IMHO, LOL, OMG and any other internet acronym you can find. I'm happy that this is fixed and hopefully it won't happen again...especially since the car has 207K on it :D

AJ



Thursday, 28 March 2013, 18:00:11.

VCDS-Lite Version: Release 1.2

Control Module Part Number: 3B0 907 551 CR

Component and/or Version: 2.8L V6/5V G 0004

Software Coding: 07501

Work Shop Code: WSC 08080

VCID: 759D62D75CD9

Additional Info: WVWPH63B53P288097 VWZ7Z0B6501119

2 Faults Found:

17831 - Secondary Air Injection System; Bank 1: Insufficient Flow

P1423 - 35-00 - -

17819 - Shareware Version. To Decode all DTCs

P1411 - 35-00 - Please Register/Activate

---------------------------------------------------------------------------





Wednesday, 16 July 2014, 17:11:53.

VCDS-Lite Version: Release 1.2

Control Module Part Number: 3B0 907 551 CR

Component and/or Version: 2.8L V6/5V G 0004

Software Coding: 07501

Work Shop Code: WSC 08080

VCID: 759D62D75CD9

Additional Info: WVWPH63B53P288097 VWZ7Z0B6501119

2 Faults Found:

17966 - Throttle Actuator (G186): Electrical Malfunction

P1558 - 35-10 - - - Intermittent

17819 - Shareware Version. To Decode all DTCs

P1411 - 35-00 - Please Register/Activate

---------------------------------------------------------------------------





Friday, 25 July 2014, 17:32:54.

VCDS-Lite Version: Release 1.2

Control Module Part Number: 3B0 907 551 CR

Component and/or Version: 2.8L V6/5V G 0004

Software Coding: 07501

Work Shop Code: WSC 08080

VCID: 759D62D75CD9

Additional Info: WVWPH63B53P288097 VWZ7Z0B6501119

5 Faults Found:

17966 - Throttle Actuator (G186): Electrical Malfunction

P1558 - 35-10 - - - Intermittent

17819 - Shareware Version. To Decode all DTCs

P1411 - 35-10 - Please Register/Activate - Intermittent

17972 - Shareware Version. To Decode all DTCs

P1564 - 35-10 - Please Register/Activate - Intermittent

17551 - Load Calculation Cross Check: Upper Limit Exceeded

P1143 - 35-00 - -

16891 - Shareware Version. To Decode all DTCs

P0507 - 35-00 - Please Register/Activate

---------------------------------------------------------------------------





Tuesday, 29 July 2014, 18:20:02.

VCDS-Lite Version: Release 1.2

Control Module Part Number: 3B0 907 551 CR

Component and/or Version: 2.8L V6/5V G 0004

Software Coding: 07501

Work Shop Code: WSC 08080

VCID: 759D62D75CD9

Additional Info: WVWPH63B53P288097 VWZ7Z0B6501119

3 Faults Found:

17972 - Throttle Actuator (J338): Under-Voltage during Basic Setting

P1564 - 35-10 - - - Intermittent

17551 - Shareware Version. To Decode all DTCs

P1143 - 35-00 - Please Register/Activate

16891 - Shareware Version. To Decode all DTCs

P0507 - 35-10 - Please Register/Activate - Intermittent

---------------------------------------------------------------------------





Thursday, 14 August 2014, 19:42:26.

VCDS-Lite Version: Release 1.2

Control Module Part Number: 3B0 907 551 CR

Component and/or Version: 2.8L V6/5V G 0004

Software Coding: 07501

Work Shop Code: WSC 08080

VCID: 759D62D75CD9

Additional Info: WVWPH63B53P288097 VWZ7Z0B6501119

4 Faults Found:

17966 - Throttle Actuator (G186): Electrical Malfunction

P1558 - 35-10 - - - Intermittent

17987 - Shareware Version. To Decode all DTCs

P1579 - 35-10 - Please Register/Activate - Intermittent

16891 - Shareware Version. To Decode all DTCs

P0507 - 35-00 - Please Register/Activate

17551 - Load Calculation Cross Check: Upper Limit Exceeded

P1143 - 35-00 - -

---------------------------------------------------------------------------





Friday, 05 September 2014, 20:56:17.

VCDS-Lite Version: Release 1.2

Control Module Part Number: 3B0 907 551 CR

Component and/or Version: 2.8L V6/5V G 0004

Software Coding: 07501

Work Shop Code: WSC 08080

VCID: 759D62D75CD9

Additional Info: WVWPH63B53P288097 VWZ7Z0B6501119

3 Faults Found:

17987 - Throttle Actuator (J338): Adaptation Not Started

P1579 - 35-10 - - - Intermittent

17551 - Shareware Version. To Decode all DTCs

P1143 - 35-00 - Please Register/Activate

16891 - Shareware Version. To Decode all DTCs

P0507 - 35-10 - Please Register/Activate - Intermittent

---------------------------------------------------------------------------





Tuesday, 16 September 2014, 19:04:54.

VCDS-Lite Version: Release 1.2

Control Module Part Number: 3B0 907 551 CR

Component and/or Version: 2.8L V6/5V G 0004

Software Coding: 07501

Work Shop Code: WSC 08080

VCID: 759D62D75CD9

Additional Info: WVWPH63B53P288097 VWZ7Z0B6501119

3 Faults Found:

17972 - Throttle Actuator (J338): Under-Voltage during Basic Setting

P1564 - 35-10 - - - Intermittent

17551 - Shareware Version. To Decode all DTCs

P1143 - 35-00 - Please Register/Activate

16891 - Shareware Version. To Decode all DTCs

P0507 - 35-00 - Please Register/Activate

---------------------------------------------------------------------------
 

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Sounds like the stepping motor was still functional when it was disassembled. Next time I have the TB off for cleaning, I'll run a thin bead of RTV in that narrow crack between motor case halves.

:beer:
 

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Moisture on the outside of the seal it's normal, and the inside looks good. What usually "kills" the TB is those contacts, they wear out the carbon potentiometer, or simply don't make good contact in all areas (like an old volume potentiometer, if anyone remembers those times). Clearly the wear occurs in the area where the TB plate spends most of it's time (idle to low load), and once the ECU has a discrepancy it sets a code and all goes south.
I am not sure if moisture killed your TB, I would say more "old age".
 

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I am glad you took it apart to figure out how it failed, but I couldn't tell from the pics that the motor inside was too rusty (it may be the device I am using).

If I were you I'd look at how the resistance changes as the contacts move across the potensiometer pads. It should be smooth and gradual. You could use your DMM probes to measure that.

Some fuel level senders have that very same problem whereby the material wears away due to friction and then resistance becomes infinite. In the case of the throttle body the ECU sees infinite resistance and tries to correct it by commanding the motor to move a little, only to read a much bigger resistance value than it expects, so it moves it back the other way.

Edit: maybe moisture had something to do with it. If it got on those pads, perhaps it helped make them softer and easier to remove due to friction with the contacts.
 

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You can also use VCDS to see how the values change, but it might be tricky to "catch it in the act" (same with the ohm-meter).
Also, the system has a fail-safe built in, one potentiometer goes up, another one goes down. Both values need to match. If at some point they don't (one of the tracks doesn't read good) it sets a code (17551 - Load Calculation Cross Check: Upper Limit Exceeded).
A lot of time it's dirt (by that I mean anything that can contaminate the resistive pads) that prevents a good electrical contact. Just by using a contact cleaner you can "repair" the throttle body. At least temporary...
 

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Discussion Starter #8
Yeah. The black dust inside the motor case was definitely the issue, or at least the biggest symptom. I think all the electrical codes were from that rust causing the motor to go apeshit. The commutator is really rusty and it was gritty spinning in its bushings.

While I don't think water got in, the fold definitely let some moisture in. The reason it looks so good on the initial photo was I'd sprayed some electronic cleaner in there (CRC). While it wasn't filthy it was surely dusty.

Car is running fantastic and the performance is better than I can remember. There's no chop when it's cold like before...especially around 1/3 throttle and it doesn't "hunt" when cruising on the highway.

happy=me

AJ
 

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Nice work. :thumbup:

I remember reading a writeup on a BMW forum where the guy had a failed TB so old he couldn't source a replacement. The resistor tracks for the throttle position sensor were worn from years of sweep arm sliding over them. Particularly the idle area. What he did was carefully bend the tip of the sweep arm so it touched a slightly different arc of the resistor track. Fresh track under the sweep arm brought the TB back to usable condition.
 

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Saw an episode of Wheeler Dealers (S13E05) where they had a Maserati throttle body rebuilt. It had worn out carbon tracks like the picture above, but the rebuilder replaced that with a contactless sensor (magnetic or optical) that will never wear out again.

Maybe an option for anyone in the UK. Really need a service like that in the US.
 

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Saw an episode of Wheeler Dealers (S13E05) where they had a Maserati throttle body rebuilt. It had worn out carbon tracks like the picture above, but the rebuilder replaced that with a contactless sensor (magnetic or optical) that will never wear out again.

Maybe an option for anyone in the UK. Really need a service like that in the US.
Great episode, and that car came out great.

Carbon wear on the tracks eh? I'm wondering if my throttle body has excessive wear on its tracks considering anytime I put the clutch in it sinks to idle, but dips as if it were to stall then catches itself. Is there a fix to that? I know for sure its not anything else because I've replaced just about every major sensor on the engine.
 

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Yeah. The black dust inside the motor case was definitely the issue, or at least the biggest symptom. I think all the electrical codes were from that rust causing the motor to go apeshit. The commutator is really rusty and it was gritty spinning in its bushings.

While I don't think water got in, the fold definitely let some moisture in. The reason it looks so good on the initial photo was I'd sprayed some electronic cleaner in there (CRC). While it wasn't filthy it was surely dusty.

Car is running fantastic and the performance is better than I can remember. There's no chop when it's cold like before...especially around 1/3 throttle and it doesn't "hunt" when cruising on the highway.

happy=me

AJ

That's great. I didn't realize you fixed it by cleaning the motor canister etc.

It looks like the TB is serviceable so anyone who has similar issues can try this.

Looking at your pics on a desktop screen it's hard to tell from the flash how worn the tracks are (certainly not the worst I have seen). I was able to fix worn tracks in another application, but it was easy to do by repositioning the PCB itself (rather than bending the copper fingers).

Did you ever find out how the weather seal came off? Did the cover get loose on its own?
 

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Discussion Starter #14
I didn't fix this TB. I replaced it with a $20 fleabay used one. The motor can was teeming with that black/rusty crap. And the comm didn't rotate very well. AFAIK, the cover wasn't loose, but it had definitely been taken off before me.

AJ
 

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Saw an episode of Wheeler Dealers (S13E05) where they had a Maserati throttle body rebuilt. It had worn out carbon tracks like the picture above, but the rebuilder replaced that with a contactless sensor (magnetic or optical) that will never wear out again.

Maybe an option for anyone in the UK. Really need a service like that in the US.
I am not sure about the Maserati TB, but I don't think that right now there is a "solid state" solution to the carbon tracks, or at least not one that will be cost effective. There are some TB in older vehicles (not DBW) that will only have switches (full throttle, idle, etc) instead of continuous feedback, but those won't work in DBW cars.
 
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