1999 BMW 528I issue, need help

[Hillamanilla3722]

I have a 1999 BMW 528I. has a fluctuating idle when started, but fine after its been run. It hesitates and lags when accelerating occasionally. Lastly, at 1/4 tank it hesitates hard and often stalls and wont turn over unless more gas is put in. Ive changed the fuel pump, fuel filter, spark plugs, and Idle air control valve. problem still exists. Any ideas what it could be?

[Lord Vader]

Possibly a vacuum leak. Inspect ALL your hoses and of course intake boot. A crack can be very small and hard to see but let in enough air to cause issues. Inspect carefully and thoroughly.

[Hillamanilla3722]

that was an option given, but easiest way to do that is to smoke the lines. I'll take a look. Thanks

[Penngwyne]

How about a blocked valve in the fuel cap?

[Hillamanilla3722]

Vacuum lines appear good, and the fuel cap would kick on the service engine light. was thinking maybe egr valve or a sensor. new fuel pump resolved the 1/4 tank issue, but still have the hesitation and rough idle at first start up.