Oh, just the defective reverse switch. They replaced the tranny in May, but the lockout for 7th gear works too well - it won't let me into 7th. Replacement to fix that issue this time, lol.

 

 

Aren't there two different sized throttle bodies?

 

for 991.1 I believe they are all the same for S and non S. But might be worth double checking, I know that is the right part for the 991.1 C2S

 

I believe they're all 82mm. I know that when I was trying to find the lowest-priced Bosch unit I also stumbled (pun intended) on an aftermarket company that takes the factory TB and modifies it to be an 86mm effective size, but I can't recall who that is now.

 

I replaced my throttle body last night with the Bosch equiv. part. While I was in there, I also fixed the brake light wiring in my wing as it became severed from age/use. I also changed the oil while I had the car apart as the filter is so much easier to get to when the wing is out of the way. Total about 6 hours of work taking my time, steam cleaning as I took things like the airbox out.

The car feels 100% completely new. There is no hesitation, no stumble. All of the jerkiness in that 2,000 to 3,000 rpm range is completely, entirely gone.

This is just one drive, about 60 km. But, the difference was immediately noticeable.

For a $200~ part, I think folks have very little to lose by trying a new throttle body. It's really not a difficult item to replace!

 

Give it some time and report back

I don't drive my 13 991.1 very much anymore but every time I drive it it feels new, throttle response is crisp and PDK is on point.

Does anyone know with time does the car's computer refresh it's driving parameters or is it all in my head.

 

Same thing here!
After 1000+ kms still fees like new.
TB was the problem!

 

Is there any data as to why the OEM throttle body is causing stumble? Is the butterfly briefly closing/changing positions?

 

For me that was the case.
I had a unstable idle...im pretty sure that the butterfly can open or close briefly and product this hesitation.
The tech tested it and found that the respond was bad and erratic

 

Just a quick update. I managed to sneak in a trip to the mountains today and did about 400 km of driving (rained and snowed on me, so the car is dirtier than it's ever been!). There are some instances of what could be attributed to the "stumble" - especially at 2,200 rpm~. That said, it's still a vast improvement over where it was before the throttle body replacement.

I'm probably going to replace the variocam solenoids as well, if anything because I just want to understand this problem as well as I can. I'll have all winter to contemplate that as I'll probably get the car put away in the next week or two.

 

I have a appointement next week to change solenoids (variocam and valve lift)
Ill Keep you in touch
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Perfect! Hope that does the trick for you.

 

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I had to change 2 of the four.. I had multiple misfire and the car was barely drivable..
BMW tells that they are wearable item..
Look at this thread https://rennlist.com/forums/991/1207...wear-item.html

 

Soler Engineering is the one company o know of who is modifying and flow testing the TB for 991.1. I am running one and am very pleased with the overall results. When I first installed it, a code was thrown but it reset itself within a few hundred km.