N54 Surging at High RPM's

[corman1]

Hello, I have a stock 2009 135 with the N54 and just hit 60k miles. I just purchased the car so I don't know its full history but I've been noticing that under load at high RPM's (like in 3rd gear) the engine seems to surge/stumble. It's not a very smooth power delivery as I would expect. When I first bought the car it did the same thing and eventually caused a SES light which ended up being a misfire in cylinder 2. I replaced the Coil and changed all 6 plugs and I haven't had the engine light since, but I still have the weird stumbling/surging in high RPMs. The injectors seems fine as there isn't any full leaking on the plugs when the car sits for a while and it starts quickly every time. I have an appointment to have the intake side walnut blasted next week and Ive ordered a new charge pipe to replace the factory one. My question is does anyone have any other suggestions as to what could be the cause of my issue? Im hoping the walnut blasting and the charge pipe will solve this issue, but I wanted to ask around for other ideas.

Thanks!

[iminhell1]

Odds are it's the dirty valves.
If it's still there after they are cleaned let us know.

[Papa13]

Normally a surge at high rpm's at WOT means the plugs need to be changed. But, since your plugs are new it could be dirty valves like mentioned above. If that doesn't remedy the problem I would look to the HPFP next. Sometimes surging is a sign its going out.

The power delivery should be smooth, not like your talking about. So, HPFP could be the culprit.. Damn fuel pumps lol.

[corman1]

Originally Posted by Papa13

Normally a surge at high rpm's at WOT means the plugs need to be changed. But, since your plugs are new it could be dirty valves like mentioned above. If that doesn't remedy the problem I would look to the HPFP next. Sometimes surging is a sign its going out.

The power delivery should be smooth, not like your talking about. So, HPFP could be the culprit.. Damn fuel pumps lol.

Originally Posted by iminhell1

Odds are it's the dirty valves.
If it's still there after they are cleaned let us know.

The walnut blasting took care of my issue!!