Tuned car pulsating between 3000 and 4000 rpm

[davemawshall]

Thank you!
I've just booked in to get my mcchip-dkr tune updated.

The tuner seems to think when I cut out my secondary cats and removed the milltek resonated section the loss in backpressure may be causing issues with the tune. In any case I have an ETS front mount coming next week so I should update the tune anyway.

Not sure the exhaust would be causing this issue but who knows - they will put it on the dyno so I'm sure they can iron out any issues while I'm there.

Thinking back I'm not sure I had this issue before I modified the exhaust so there may be some validity to this.

Going to check / clean MAP sensor and test the boost solenoids in the meantime

Will check in after done!

[E30 Racer]

Good luck and report back with your findings!

[kiysersosae]

I finally got my issue sorted with an updated tune, I think. I'm still pushing 18.psi so whatever they have done to the tune file its sorted it out. Someone mentioned on another post, vans timing corrections to sort the problem!

The Only other thing it could have been was the charge pipe on my car had some metal loss around the throttle body housing, probably due to the movement of the engine on throttle and braking. I was assuming that maybe some charge air was escaping at high pressure and causing incorrect readings on the inlet manifold sensor. I fixed this while i was waiting for my tune file so it's hard to tell which one fixed my issue, but I would recommend you check your charge pipe.

[Trond]

I met another BMW 1M owner recently with a tune (forgot which tune it was) and who also had this surging issue from around 2500-4000 rpms. In his case the surging started after changing the whole exhaust system with catless downpipes. Afterwards the tune was adjusted and problem solved.

[MT135]

I had this on my N54. Replaced every part under the sun until it was discovered to be a back end flash running w/out the JB4. Tuning issue.

[Xaeryan]

Originally Posted by MT135

I had this on my N54. Replaced every part under the sun until it was discovered to be a back end flash running w/out the JB4. Tuning issue.

Can you elaborate a little bit on this? So you resolved it by using JB4 on top of the BE flash?

[MT135]

Originally Posted by Xaeryan

Can you elaborate a little bit on this? So you resolved it by using JB4 on top of the BE flash?

My car had JB4 and BE flash.

JB4 was removed, surging issue became present.

Surging between 3000-4000 rpms has been documented in cars that were tuned and reverted to stock. Would suggest a "fresh start" to your cars DME.