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popping sound and code p0171

Been having a lot of problems with my 3.0i. I've changed loads, and had the car in bits to find the original codes p0171 and 0174.
After changing nearly everything, I only have p0171 but I get a popping sound through my intake.
Where do I look now?

Perhaps it's time to replace the seals for the intake manifold. A P0171 is a code for a lean condition. Old seals could be allowing air to leak into the intake manifold.

+1 , also check any of the intake elbows, anywhere you have unmetered air entering the system after the MAP/MAF sensor you will get a lean condition.

i have replaced the intake elbows already, and all vacuum lines. I just bought the inlet manifold seals, and go from there.
many thanks

Quote:

Originally Posted by trader4 (Post 1036534)

I don't understand how a vacuum leak would cause a popping sound.
Do you have the diagnostic software that shows how well each
cylinder is firing? Maybe something wrong with a valve on one cylinder?
Also possible the popping isn't related to the lean condition. Did you
remove the DISA and take a look at it? Loose DISA vane can cause
a nasty rattle kind of sound.

This also might be one of those things where it's worth paying a BMW
dealer an hour for an opinion. A trained ear beats tearing the car apart,
IMO.

Check out wiki as to why a lean condition can cause a popping sound ( backfire) through the intake manifold.

Back-fire - Wikipedia, the free encyclopedia

Is it a steady popping?

Manual trans?

Thrown a low gear and over-revved?

Bent valves?