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Discussion Starter #1
Hi all. I just wanted to say thanks to everyone who has offered DIY information on the S65/S85 throttle actuators.

I was getting a persistent P1628 and it was seriously hanging me up on the way home from my mom's house several hundred miles away. To the point where I was filling it up with the engine running...bad practice, I know, but if I stopped the engine it was unlikely it'd start properly again. So I went ahead and smoked a cigarette and talked on my cell phone at the same time as I fueled up. I figured if I'm gonna live dangerously, let's go for broke! (That's not really true)

Frighteningly, while I was filling up at one point, the engine revved up to maybe 2 or 3k...on its own (thankfully it was in neutral) and when I got back in it the redline was down at 4.5k, aka limp mode. Oddly, it did restart correctly. I guess these things have lots of failsafes to protect against unwanted acceleration...maybe they didn't work this time? Maybe it was because the gas cap was off. Who knows? I'd never had it go into limp mode while running.

Because I only ever got the one code for bank 1, and I'd already spent money on new gears, and I don't mind putting in the time, I opted to buy a rebuilt TA from Abdul over at Mpower motorsports for bank 1, and replaced the gears on the one for bank 2 that never gave me any trouble, in the hopes that I'll at least put off its failure a bit longer having properly functioning gears installed, hence, I suppose, taking some of the undue stress off the FETs. Its gears were definitely worn. Incidentally, apparently Abdul's family has suffered a real tragedy. Keep them in your thoughts. Not my place to say what, but suffice it to say it's many people's worst nightmare.

Anyway, I put it all together and it works like a charm and my throttle response is a bit more spritely. We'll see how long bank 2 hangs in there.

Anyway, this site has been a wealth of information and I'm most appreciative!
 

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Have you or anyone else had an actuator failure around the time your battery voltage was super low? Enough to start the car but very low voltage... had mine happen on start up. Never had a code like this before that. And its Only on one side

if i change the gears and all mosfets on the one that hasn’t thrown a code — will it last a long while? What about the dead one... I read that even replacing mosfets won’t work most of the time if a code was thrown
 

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Discussion Starter #3
I have not experienced the battery related issue, although I’m certainly familiar with how low voltage from the battery can screw with the systems in a BMW.

As for whether replacing the gears and the MOSFETs in the one that hasn’t thrown a code works, in my case it’s just an experiment because I already had the gears. I did not replace the MOSFETs in mine. I am doing all the work myself, so I’m not worried about paying for more labor to have the second one done. And now that I have done it once, I believe it’s something I could do in a matter of a couple of hours. It’s actually super easy, as BMW DIYs go, IMHO.

Someone on this board, in some thread, made the comment that electronics don’t wear out… They stress out. I know that to be true. What I don’t know is whether the components in the throttle actuator are sufficiently derated. As in, I don’t know how close to the edge of their capabilities BMW tries to run them. Hence, I don’t know how stressed they are under normal circumstances. But I do know that sticky throttle linkages, and worn gears put even more stress on the electronics in the throttle actuators.
So, anecdotes aside, logic would dictate that changing only the gears in a throttle actuator that has not yet thrown any codes would at least yield a bit more usable life.

That said, it is still a game of likelihoods, and only changing the gears is not considered a long-term fix. Even doing the MOSFETs is not a sure thing, from what I understand. I still fully expect the other one to puke before too awful long.

In my case it made some sense to go ahead and kick the can down the road a little. But at the end of the day my feeling is that the smartest, easiest, and least expensive way to get working throttle actuators is to buy a couple from Abdul at M power Motorsports and call it a day. Then start saving for new rod bearings.🤦‍♂️
 

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Discussion Starter #4
I should clarify that regarding wear and tear on electronics, electrolytic capacitors DO go bad but they’ll do that even if they sit unused for a long time because the chemicals within them break down.
But I don’t know if there are any in the TAs. I don’t recall seeing any but I wasn’t looking for them.
 

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Apparently there is one 2200uf cap on the opposite side of the board

i would like to find out exactly the kind of cap it is so that i can order part ahead of time and replace it
 

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Discussion Starter #6
The voltage should be marked on the side. Probably should try to establish model and manufacturer in case they’re counting on an ESR spec or something. Definitely want a 100degC part.
 

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The voltage should be marked on the side. Probably should try to establish model and manufacturer in case they’re counting on an ESR spec or something. Definitely want a 100degC part.
any other parts i should replace as PM while im replacing/fixing the actuators? i was going to replace the 2 breather valves and water thermostat since they’re cheap. What about the Throttle position sensors? Do they fail often as well or do they last a long while?
 
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