Mass flow sensor problem

[m3f_vm170y8]

My 99' M3 has 50,000 miles on it and I've had it for a year with no problems. It sat for a week or two and when I went to start it up, the battery was completely dead. I just bought a new one 5 months ago. I charged it over night and it started fine. I went for a ride and it was idling funny and starting to stall. I got it home after stalling a few times. Would only start if you gave it gas. I have a peake code reader so I checked it and it read code 8(mass air flow sensor). I removed it and checked the rubber boot for leaks. No leaks. I ordered a used one with a guarantee and when I got it, it had the same problem. When you turn the ignition key on, there is also something clicking,just to the left of the mass air flow sensor if you are looking in the hood. Might be another problem? The car will still start but you have to give it gas. I am currently waiting for another mass air flow sensor and am hoping I just got a bad one. It was $40 with a 90 day guarantee vs. $400. Anyone had this problem? Is the battery problem anyway interconnected? Doubt it! Any help would be appreciated. I also have a drop in K&N air filter which I have read causes the MAS to go bad. I have not oiled it for about a year, so if it is the MAS, it should be fine when the next one comes ? Any help appreciated.



Thanks

John Beyrand

99' M3

06' Yamaha R1 50th Anniversay streetbike

04' yamaha R1 racebike

01' YZ-426

05' Yamaha Zuma

[m3f_Sirius]

Try cleaning it with MAF cleaner. CRC makes some.

[m3f_97BLKM3COUPE]

Sounds odd that the car will not start. Are you sure it is because of the battery. There is another issue that can cause a rough idle/stalling while not on the gas AND the car will be difficult to start. Lets not get into that now and hope it is a bad MAF.



It happened to Sirius's car before he bought it (I think), luckily he got a car with a brand new engine.

[m3f_Sirius]

My engine was exploded on the track, but not by me. :P

[m3f_vm170y8]

the car will start, you just have to give it gas and it will not idle. I will let u know how it goes when the new used MAS gets here.

[m3f_screaminM3]

Sounds odd that the car will not start. Are you sure it is because of the battery. There is another issue that can cause a rough idle/stalling while not on the gas AND the car will be difficult to start. Lets not get into that now and hope it is a bad MAF.



It happened to Sirius's car before he bought it (I think), luckily he got a car with a brand new engine.

And what would that issue be?



I'm wondering if the contacts to your MAF could be corroded.



Another thought: has your alternator gone south? That might explain the drained battery and rough running. Is your battery keeping its charge or has it run down again? Anyone know if a bad alternator can cause the DME to throw a MAF code?

[m3f_PhYrE]

Sure you don't just have bad gas? I know maybe a simple problem, but if you filled up recently it may be something to look at. Maybe fuel filter is clogged as well. Just seems a bit strange that it can't even run at idle.



-M

[m3f_97BLKM3COUPE]

And what would that issue be?

Have you had any problems shifting before this happened?

[m3f_morerevsm3]

check voltage of middle wire on throttle position switch, should be 0.4-0.5V at idle position

[m3f_bigneil]

Are you sure it's not installed backwards?


Mine idled like crap when it was backwards.

[m3f_vm170y8]

the battery has held its charge. I have another MAS on the way. It is throwing a code 8. Could bad gas really cause that? I will wait to install the new MAS and let you guys know. I was really wondering what was clicking just left of the MAS when I turned the ignition key on.



Thanks

[m3f_PhYrE]

the battery has held its charge. I have another MAS on the way. It is throwing a code 8. Could bad gas really cause that? I will wait to install the new MAS and let you guys know. I was really wondering what was clicking just left of the MAS when I turned the ignition key on.



Thanks

Possibly your EVAP valve.



-M

[m3f_vm170y8]

that is what is clicking. I will check on it. Also, it gave me a EVAP code error along with the MAS code error. Thanks

[m3f_vm170y8]

This is really weird. I turned the ignition on to hear the clicking and it wasn't clicking. I installed the old MAS for the hell of it and cleared the check engine light. Started it, won't idle, and took it down the road. About a half of mile, it started running real rough and the check engine light came back on. Went home, checked the error codes. MAS and #1 cylinder misfire. Great, I thought. Again for the hell of it, i reset the check engine light. I tried starting it and not only did it idle, but seemed to run fine. Took it out again, about 10 miles, adn filled it with fresh fuel, and it ran great. Got home, shut it off,then on. Perfect. I don't consider myself a BMW mechanic, but I should look into opening my own shop if I'm this lucky. I guess I will try it tommorow. Let u know what happens.



Thanks

[m3f_shreker]

Did you ever find out what the problem was?