Another Throttle Actuator Failure/Tear Down/Attempted Repair - BMW M5 Forum and M6 Forums
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post #1 of 56 Old 11th July 2016, 02:09 AM Thread Starter
Niart906
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Another Throttle Actuator Failure/Tear Down/Attempted Repair

So it's my turn to experience a throttle actuator failure. My M5 is a March 2006 build SMG car with 94,xxx miles, based on the date stamps on the actuators themselves, these are the original units that came from the factory. Seeing as how these are obscenely expensive for what they are (read: poorly designed POS's), I thought now would be a good opportunity to try some of the fixes outlined by fellow board members. Unfortunately, so far I haven't found a fix and I'm looking for some feedback.

My failing actuator only caused my car to go into Limp mode after a restart, once the engine was warm. If I cleared the codes and waited for the engine to cool down, the car started and drove fine.


Post Intake Manifold Removal:
I examined the throttle linkages and opened and closed the valves by hand, I found that my car had the typical squeak other members had reported. Both banks had significant resistance when opening by hand. Part way through their travel you could feel them hang up due to dirt/lack of grease. I took the time to lubricate all of the throttle bodies to help relieve some of the stress on the actuator motors and gear assemblies. They actuate much smoother now, no more hang ups while moving. Moving forward I'd opt to re-lubricate these anytime the intake manifolds are removed.



Video:
Untitled by Jonathan Santarsiero, on Flickr

Pre Tear Down:



Examining the gears:

I expected there to be significant wear considering these are original to the car. What I found was next to no wear on the white center gear, and the typical tooth thinning on the half moon spring loaded gear. I forgot to snap a pic of the reduction gear, but there was very little wear to be seen.

Lots of dust I assume from the gear wear...






The Electronics:

I found some slight discoloration on one of the MOSFETs on the failing actuator. So I opted to try and swap that out seeing as how a few members on M3post had reported success doing so. Unfortunately, this did absolutely nothing. The slight discoloration seen appears to be from the coating applied to the board at the factory, not from a failed component.












Next, I'm considering having the DC motor rebuilt, but my gut says this is another failed component on the board. Any idea what component(s) would work fine when cold and then fail when hot? I still haven't replaced the gears but I'm not convinced new gears would remedy it at this point.

2013 F30 335 Estoril Blau II/Black (Current)
2006 E60 M5 Silbergrau Metallic/Indianapolis Red (Sold)

Last edited by Niart906; 11th July 2016 at 02:11 AM.
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post #2 of 56 Old 11th July 2016, 03:16 AM
jcolley
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Typically if the MOSFET goes, the circuit which drives the gate lead on the MOSFET becomes damaged as well. None of the motors I've seen were damaged beyond use, including brush wear. There is a decent amount of carbon dust built up (due to the enclosed can) which alters insulation resistance, but not to the point of reducing motor torque or increasing the current ramp integral the control board reports on.

Ridiculous design. No circuit protection for the most likely means of failure, just a monitoring routine to say it happened.
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post #3 of 56 Old 11th July 2016, 01:01 PM
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That MOSFET was not damaged. The 'discoloration' was simply bunched up & aged conformal coating on the PCB.

Maybe I should get back to this topic some day and finish my job. I am so close to understanding it.
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post #4 of 56 Old 11th July 2016, 08:34 PM
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Good to see another member going after this issue. These things are annoyingly expensive for such a non-robust "wear" item...

Hopefully a fix will come out soon!

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post #5 of 56 Old 11th July 2016, 11:12 PM
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My 2nd actuator just went out on me last night.... Does BMW put this **** on a timer or what? tired of paying their insane prices for a dumb actuator. Does anyone have a better source for replacements?

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post #6 of 56 Old 11th July 2016, 11:24 PM
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I have two of these circuit boards from TAs that I recently replaced. With one of them, when I push the little lever to activate the gears etc, it moves fine in one direction but drifts back to rest - like a short in a single direction - maybe something involving a diode(??) The other one is better but fails one of the ISTA tests (the 2nd attempt only). That's enough to make it persona non grata with the car software.
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post #7 of 56 Old 11th July 2016, 11:25 PM
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I have the VDO actuators for $625. I can't keep them in stock, but have an order in with two coming this week.

I hate plugging them here, but it's the cheapest I can source them anywhere and still working on a better design.
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post #8 of 56 Old 11th July 2016, 11:26 PM
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Quote:
Originally Posted by pizdous View Post
My 2nd actuator just went out on me last night.... Does BMW put this **** on a timer or what? tired of paying their insane prices for a dumb actuator. Does anyone have a better source for replacements?
Try fastattackmotorsports.com (JColley) or spareto.com if your credit card or paypal can do foreign currencies.
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post #9 of 56 Old 12th July 2016, 12:25 AM Thread Starter
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Quote:
Originally Posted by jcolley View Post
I have the VDO actuators for $625. I can't keep them in stock, but have an order in with two coming this week.

I hate plugging them here, but it's the cheapest I can source them anywhere and still working on a better design.
Jim, please let me know once you get them assuming they aren't spoken for. I'm getting sick of seeing this car sit and might be interested in taking one of them off your hands.

In the meantime, I'm going to try and remove my bad actuator and have another look at that board. Considering how cheap the majority of these components are, I may just continue to swap questionable pieces out until we narrow down a culprit.

2013 F30 335 Estoril Blau II/Black (Current)
2006 E60 M5 Silbergrau Metallic/Indianapolis Red (Sold)

Last edited by Niart906; 12th July 2016 at 12:26 AM.
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post #10 of 56 Old 22nd July 2016, 07:38 PM Thread Starter
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No real updates yet. I just placed an order with Jim's company to get a brand new actuator so I can actually drive the car occasionally.

I may try and bake the electronics from the bad actuator like others have tried with a failing graphics card from a computer. The heat should help reflow the solder joints. Figure it's a $600 paper weight to me now, so I can't really make it any worse.

Additionally, my car now enters limp mode immediately after a cold or warm start. Strange that it would go from being somewhat temperature dependent to just completely not working now.

2013 F30 335 Estoril Blau II/Black (Current)
2006 E60 M5 Silbergrau Metallic/Indianapolis Red (Sold)
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