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BMW E36-E34 M50-M52 Loss of Power, Surging Idle, Whistling Noise – 323i, 325i, 328i, M3, 525i

April 26, 2011

This answer is applicable for many BMWs in addition to the one listed below.

car year: 1994
car model: 325is
Hey,i have a 1994 325is m technic that’s been acting weird lately. sometimes when its cold and i push on the gas it delays the car from actually moving. my mechanic said it could be the fuel filter or the fuel pump. i haven’t had the time to check either. now about the loud whistling noise coming from my intake. i replaced the intake boot, because the one that was on there was bad. for the first coupe minutes the noise went away. the car does have problems idling every now and then but it stops after a few seconds and goes back to the normal idle rpms.

The lack of power that you are describing, may indeed be due to a very dirty fuel filter or weak fuel pump …. along with many other possibilities. Let’s first take a look at the whistling noise. This would typically be due to a vacuum leak in the intake system (and certainly could contribute to your lack of power issue). We need to fully inspect all of the boots bellows and hoses that carry air, to include; crankcase ventilation hose and check valve (from valve cover to back of intake manifold), intake boot (which you have replaced), the two hoses that connect to the underside of the boot, intake manifold gaskets, etc. If, after a thorough inspection, nothing is found, we would suggest having the intake system “smoke tested”. This involves injecting a smoke (under pressure) into the intake system and watching for any areas where the smoke may leak out.

Let’s track down the potential vacuum leak …. then see how the other issue is doing. Just give us a call at 800-535-2002 once you have your vacuum inspections set and we can order up any parts that may be needed.

Intake Boots, Hoses and parts:

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