dhaf

Hey all - I have a 2008 LCI 535xi that I bought certified 1 year ago as a CPO - it's totally stock, no modifications (other than LED AE's from John @ Motorcepts). Over the last couple of months I have really felt a difference in how the car drives. Some days, when I start the car, it feels super laggy and heavy. There's a 5 second plus lag between when the car actually moves vs. when I press the accelerator. The engine drives slow and sluggish. Other days, it's much better - still doesn't have as much "go" as when I first bought it - but it moves better and the lag is much less. I've taken it to two separate dealerships, there are no issues that pop up, no errors that they are able to catch. I've taken it to an independent BMW repair shop (they have a great rep) who are doing a manual inspection. The mechanic drove the car and felt what I described above - it drives really sluggish/laggy. However, there are no error codes, nothing that stands out. At this point, he's taking an exploratory look at the intake valves to see if there's any build-up there; he said it may be the initial phase of carbon buildup but he can't tell because there's no codes.

Anyone have any experience with something similar to this? Any advice?

Thanks in advance.

louisrai

waiting to see what the others say....

Shydee

Sport mode usually solves my lag problem.

dhaf

Just heard from the mechanic - apparently there is a ton of buildup in the valves. For a car that only has 30k miles, that's really strange to hear. I'll let y'all know when I get it back and if this solves the problem.

sahiljain22

Ask your mechanic for a picture and post it . Then goto the dealer and demand some free engine cleanup.

I could imagine the buildup being on a 80-90k run car, but 30k is tooooo less.

pukka

This can happen after prolonged use of lower octane gas.

dhaf

Unless the previous owner used low octane gas, and the dealership didn't do their job with the certification, that isn't applicable - I only use premium gas when filling up (minimum 93 rating). Good thought though - making me think more and more that the dealership just didn't do their job.

Shydee

I believe 93 octane gas still gives you carbon build up.
Lots of people with n54 engines are starting to clean them with walnut blasters.
Have your dealer clean it up for you.
But im pretty sure itll cost you.

Jim165

Fuel type/octane makes no difference in a direct injected engine like the n54/55. The problem is there is no longer any fuel cleaning the backside of the intake valves like in a port injected engine. Unless you have a Toyota direct injected engine, this problem is inevitable...hence one of the many reasons I purchased a 550i...

pukka

Good point - but the problem may not be the Direct Injection engineering but rather the timing of the fuel injection during the 4 stroke cycle which is one of the reasons why high octane fuel is required.