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Turbo lag after cleaning valves
Posted to Technical Discussion Forum on 12/16/2012 3 Replies

[2007 BMW 335i, Emissions Photo] [2007 BMW 335i, Emissions Photo] Hello, I have my neighbor's 07 BMW 335i in my shop for a noticeable or perceived turbocharger lag while accelerating. I notice the problem when accelerating on to the Highway from an on ramp and while at cruise speed and trying to accelerate for passing. When accelerating from cruise speed of 50-60 mph the vehicle is hardly moving faster, then 3 seconds later I can feel and hear the twin turbos spool up and I have power.

My neighbor caused this problem, so it's not my problem:) He found on the web how he can clean his intake valves himself. He removed the air box, throttle body and plume. With the intake valves now exposed, he would turn the crank by hand to close the valves and while closed, he filled the head chamber with a cleaner and scrubbed around the valve with a tooth brush (his or his wife's, I didn't ask). When finished, he cleaned out the camber with a shop vac. He also cleaned the throttle body and plume. He reassembled and installed new spark plugs. Manifold gasket and spark plugs were OEM. He states the vehicle idles better and feels smoother, but now has this lag.

I normally do not work on these platforms, but I would takes a cursory look at it. Test drove and confirmed condition. Scanned vehicle with Modis and DS708 and found no codes and long/short term fuel trims close to 0. My underhood inspection found this vacuum line disconnected. This is part of the engine driven vac system . Ok, found the problem, nope, still have this lag. So far I only removed the airbox and everything appears fine, everything connected. Smoked checked engine driven and engine vac systems and found no leaks.

Monday I'm going to take a test drive with another tech to watch the PIDS.

Any key pids I should be looking for? Any ideas how my neighbor caused this problem when the vehicle drove fine before this worked on it?

BTW, I have not had a chance to figure out where or what systems the vac line I did repair affected. The rubber line on top of the airbox was disconnected from the hard plastic line. This is on the driver's side and the rubber line goes into the wiring harness running along the left fender. Any ideas?

Thanks for reading my post

Dwight Bresemann
LSI Automotive
Oceanside, California, USA

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car Vehicle Data

2007 BMW 335i 3.0L

Engine3.0 L
Trans6-speed Standard