Have you thrown any codes?

 

confused....will a bad MAF cause poor acceleration? why

 

^ Because it controls the fuel/air mix in the engine?

 

I have had poor acceleration for a couple months, and it finally and consistantly kicked out the following codes yesterday...
- P1397 cam shaft position sensor.
- P0101 mass or volume air flow circuit range performance problem.
I replaced the exhaust side cam position sensor and cleared the codes...no new codes have appeared.

The reason for suspeting a bad MAF is that I got a P0101, and when I disconnect the MAF, my 0-60 time decreases by 2 secs. I am not rushing to the dealership to spend $300 for a MAF because I haven't come across an article where a defective MAF will cause acceleration problems; it idles fine and is not misfiring.

Please let me know if I should be looking at something else.

David

 

volumetric efficiency. I posted the link to download the tool and how to use it

 

My maf is apparently bad, the engine light keeps going on and off. The dealership said it's malfunctioning. My acceleration has not been effected since it started throwing a code for it...weird. That's why I haven't changed it lol.

 

simple yet effective test....

If it is a bad MAF you will most likely have a shitty idle....

Test for a bad MAF: Unplug it, drive around for a bit and see if the car performs better. If it does, bad MAF. If not, then there's another problem...


And before the thousands of don't do that it'll F^ your car post come in. Your car runs off of redundant systems. A.K.A. it is designed to run off of the map sensor in the event the MAF fails. I wouldn't recommend leaving it unplugged for more than just this simple test but that's because a bad MAF is better then no MAF

 

so much wrong with this info I don;t know where to start. BMW DOES NOT use a MAP sensor. Disconnecting the Maf does put it into know values but that does NOT tell you if the Maf is the issue

 

My idle is fine but the acceleration is really bad. I'll try the MAF test mentioned above this weekend and see if it tells me anything.

 

I feel you krauseda. I'm on the same boat and I dont really know why. My idling is fine but when i press pedal, seems like it's slow.. :hmm::hmm:

 

Have you tried actually cleaning the maf? Mine fouled out before and I picked one up from the junkyard for like 50$, cleaned it, and been fine ever since.

 

Bad acceleration could also be a vacuum leak? Have you checked your intake boots and do you get any whistles under hard acceleration.

 

My method may not be the best most technical way to do it. But most people don't have acesses to the equipment needed to run a ful diagnostics. You may not like this method, you may not think it will work. That is not my problem. I have used it on two cars, with sucsess of diagnosing a failing MAF. However, I will state that these cars were dealing with rough idles as well as other factors. When the maf was unpluged and the car was cranked it idled fine. Plugging the maf back in yeilded a bad idle again. Thus, the maf was the problem.

I'm not trying to say that this is the best or only way to check a MAF but, for the average enthusiast, this is the only method I know of rather than paying a shop.

Finally, if my method is so wrong or useless why have you not posted the correct way. I don't doubt your skills as a mechanic i simply ponder upon the fact that you say I'm wrong yet provide no evidence of why. True I have provided no evidence that it will work other than past experience but the OP can test my method and yield a result (whether possitive or negative). However, you negate my solution and offer no path in return. simply is seem to be leading towards action where you seem to state do nothing.

 

Finally, if my method is so wrong or useless why have you not posted the correct way. I don't doubt your skills as a mechanic i simply ponder upon the fact that you say I'm wrong yet provide no evidence of why.

I know I've already posted why your "method" is completely wrong. All you had to do was search through Seth's threads to find the correct way to test a MAF:

http://forum.e46fanatics.com/showthread.php?t=617788

 

I still won't say my method is completly wrong, however, I will say the method he posted is a better way to test.

I've used my method when a bad idle was present. Making the car rich wont make it faster or nessicarily help the idle.

 

There is a post in Neils link where someone unplugged the Maf and the car ran better but the MAF WAS NOT the issue. Trust me that test is not anywhere accurate enough to relay on

 

My first post in this thread said how to do it. I just said search As I posted the file and instructions and info on this before. You don't need any real advanced tools to check it right. Some of it can be done with a multimeter

 

http://www.ehow.com/video_5225929_mass-air-flow-sensor-bad.html

 

Hello JBEurotech,
I see many responses where the MAF sensor fails and car keeps on running/driving. I just had a MAF sensor fail, and the accelerator pedal was disabled. 02 Manual 330CI. Car stays in idle and it will not let you rev up the engine.
Why some BMW allow it to continue running and others do not?

 

I bought a new MAF sensor for $61 at 1A AUTO http://www.1aauto.com/?gclid=Cj0KEQ...zBRDezri2r6bz1qYBEiQAg-YEtoY3TRH-msf0CUeuf2EpvpoAcWXVoGLBYseQOxdUyHoaAkfr8P8HAQ
(866) 404-3393. 1 YEAR WARRANTY. You can buy them cheaper on eBay but you can call and talk to these guys. They ship free and assured me they'd replace it if it failed. I figured I'd try it rather than spend $200+ on a Siemens VDO unit that may not cure the problem. It DID solve the issue and the car runs great now.