[-CMS-]

Hi guys,

I'm having an annoying issue with my 2009 335xi 6MT, which has persisted since I bought the car last summer. The car has clocked around 110,000 miles.

If I go near WOT in high gear (e.g. 5th or 6th gear at speed of 50-60 mph, with RPM at around 2000), the engine rumble increases gradually (in relation to throttle increase) to the point where at near WOT it cuts off power in a constant jerky way. The jerkiness feels slightly similar to traction control cutting power to the wheels, but with a much stronger jerkiness to it.

Alongside this, I do get small hiccups at idle - the usual small jerks and shakes - especially when the engine is warmed up.

No problems at all at higher RPM's, the car pulls nice and strong, and no misfires at all.

Turbos have been replaced approx. 62,000 miles ago along with the HPFP. Plugs (Bosch OE) and coils (Bremi) are a few weeks old, and have been replaced in connection with doing a complete intake walnut blasting. Injectors are originals (as far as I know), but no evidence of leaking in the plugs.

As for mods, I am running JB4 with an MHD back-end flash, an aluminum charge pipe, removed front cats and K&N filter in the original air box. I use 98 RON (93 pump I presume) together with 10 liters of E85 (85% ethanol), which the car is mapped for. I do get the same issue running only 98 RON.

Any ideas on what could be causing this would be greatly appreciated. I'm debating whether looking into my VANOS solenoids, as these have never been replaced to my knowledge, and would to my best understanding cause symptoms at lower RPM's, especially at higher loads. I would also expect the car to have more low-end torque than it currently has, which would also support my VANOS theory.

Cheers guys and my apologies for the lengthy description...

[type-dRew]

I had this happen and it was plugs after I did a walnut blast, you already did that so im unsure.

In for ideas.

[-CMS-]

Will go under the assumption that it’s clogged VANOS solenoids and clean them up. I’ll report back. Other possibilities are fuel injection related (seems unlikely) or problems with the transfer case.

[Aceway]

Buy some NGK's and gap them to 0.022".

[-CMS-]

Originally Posted by Aceway

Buy some NGK's and gap them to 0.022".

I doubt changing plugs to NGK's would make a difference, considering my current plugs are OE's and brand new. New plugs vs. old ones, yes. New Bosch vs. new NGK with my very moderate level of tune, not likely.

I would understand if I ran a high tune on my car. But currently I'm limited to approx 380-400 BHP mainly due to limitations of the transfer case, i.e. I don't want to blow it apart.