125i N52: Shuddering under load, unstable RPM at no load in part throttle

[HeavyJ251]

Hi All!
Long time listener first time caller ☺️

I’ve come into possession of a 2011 125i Convertible, and I think it’s a great little car. Having only owned E36s in the past, I have to say it’s a bit of a different animal.

Anyway, I’ve noticed the following symptoms:
While climbing a hill, part throttle, medium to high load, just below 1500rpm the car shudders. Under light load, it’s like someone is pulsing the throttle, with the occasional shudder.

I thought I’d see what happened in that RPM range while under no load (in neutral, not moving), and it was very hard to get it to that range. It either wanted to overshoot it or sit below it.

When I did manage to get the pedal just in the right position, it hunts between 1300 and 1500rpm, like it can’t hold 1500, comes back down, settles, and goes back to 1500, only to come back down (lather, rinse, repeat) indefinitely.

I know my pedal wasn’t fluctuating as I was looking at the pedal position on BimmerLink, and it was steady.

My thought is that the two problems are related, as well as the acceleration at part throttle feeling a bit inconsistent and ‘lumpy’.

Quick version:

• Shudder at medium/heavy load at 1300-1500rpm
• No load/Neutral: RPM jumps between 1300-1500 at part throttle, doesn’t want to hold 1500rpm

No error codes found… I don’t know where to begin looking! Any help would be appreciated I’ve searched the forums but nothing sounds quite like what I’m experiencing.