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Discussion Starter · #1 ·
I have a 98 M3 and just replaced the alternator. I let my battery charge for fifteen minutes or so before I started it after the replacement, it started but the alternator was making a very loud whine noise. I figured it was just working extra hard to catch up. I let it run for ten minutes or so before shutting it off and wondering if something was wrong. I put the battery on a drip charger for 2 days until it was full and tried starting it again. It started this time and sounded completely normal, running through it's normal warm up cycle. After it went to idle at around 700rpm i tried to rev it but it just boggs down and kills. After a few times of this i got it to rev, but it was way behind and super sluggish. 99% of the time it just kills when the gas gets pressed.
I also replaced my air mass boot, i'm wondering if that could have anything to do with it. Any ideas would be very welcomed, I'm trying to get home for Thanksgiving!
 

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Sounds like a vacuum leak. Check that everything has been connected on your boot. It is amazing how bad an engine will run with a massive vacuum leak.
 

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Sounds like a vacuum leak. Check that everything has been connected on your boot. It is amazing how bad an engine will run with a massive vacuum leak.
Took the words out of my mouth. Loud whine and a replacement boot .. .definitely sounds like a clamp isn't tight enough or you forgot a vacuum hose somewhere.
 

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Another thing to check is if you have dislodged something on the Air Mass sensor. try disconnecting it and see if the engine behavior is any different, If it is, try cleaning the element with some brake cleaner. Good luck
 

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Discussion Starter · #7 ·
drive belt is on correctly. I checked all the clamps but i will double check them. Will post later on results
 

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Discussion Starter · #8 ·
I've checked all the vacuum hoses and sensors, everything seems to be tight. I'm gonna mess with the mass air tomorrow. If the drive belt were routed incorrectly it wouldn't start and run normal until i push the gas would it? I'm almost positive it's on correctly, but I don't wanna take the fan off again unless it's worth checking
 

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Discussion Starter · #9 ·
Another thing to check is if you have dislodged something on the Air Mass sensor. try disconnecting it and see if the engine behavior is any different, If it is, try cleaning the element with some brake cleaner. Good luck
I didn't disconnect the air mass sensor, but i removed the entire mass air flow cylinder without removing the electrical hooked to it. As soon as it was unhooked the car started, revved and idled completely normal. I put the air mass boot/intake/air mass sensor back on and it goes back to the same old problems. So obviously the issue is centered around the air mass sensor.
To clean the sensor do i just spray it down with brake cleaner and wipe it or what's the procedure?
 

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Discussion Starter · #10 ·
Brake cleaner will work to clean it? I've read a couple places not to use anything but electrical contract cleaner, but final say is gonna come from my trusted Bimmerwerkz community.
I have brake cleaner available and electrical cleaner has to be purchased.
 

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Since no one with actual first hand use has replied, I will try to help. I only have "book learning" on this. You can buy MAF spray cleaner. You spray it and make sure you get the actual air metering part. DO NOT TOUCH the fine wires or you will be buying a new part.
 
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