2008 X3 3.0is 137k - 0-20 throttle surges and seems to lag until over 20 mph.

[txtorquemade]

Very frustrating symptoms.

From 0-20 or so, the throttle lags, then surges until over 20-25 mph, then runs fine. Idles fine, does not die or misfire. Does seem to lag some when in the lower end of power band.. 20-40 mph. No engine noises.

I just can't tell were to go with this. I do some wrenching mainly on e30s, e46s, e36s.. etc. but this 'feel" like a tranny slip, but no lights or other indications of trans problem.

Any ideas?

[z3forlife]

May have a vacuum leak. You could have a mechanic smoke test it for any leaks or build one and do it yourself. Do you know anyone with a bmw code reader ?

[txtorquemade]

UPDATE: Last night, the SES light comes back on, the car starts missing, idling bad and making a loud, whining noise in the engine, worse at idle, and never stopped. Had to drive home and barely made it. Lack of acceleration, missing, etc.

Camshaft/ crankshaft sensor? But what was the weird noise? Even more confused now.

[Shock Loaded]

The vacuum leak just got a lot easier to find... check yourpcv system or possibly the big hose on the rear of the valve cover.


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[txtorquemade]

CCV system?

[z3forlife]

A bad ccv will make it smoke too and use oil. Go to the z3 forum and look for the z3 diagnostic thread. You can download inpa software to a laptop and have a factory code reader once you get the 20pin cable

[txtorquemade]

I resolved the problem. The air duct from the air box to the intake throttle body was disconnected from the throttle body. ALL that unmetered air now measured!!

Is like a whole different vehicle.