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Old 03-22-2011, 10:41 PM   #1
28firefighter
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Bad MAF? More confused than ever.

So after having my fuel pump and filter replaced, I'm still having issues. What I initially thought was unrelated all seems to be adding up to what I think is a bad MAF.

Here are my symptoms:
Erratic idle and idle dipping

Sluggish acceleration

Slight...skip...in 4th gear between 1500 and 2000 rpm.

Engine bogging between 2k and 2500 rpm when at higher speeds or trying to get there.

The car has no codes lighting up or pending. It has no vacuum leaks either. Here is a list of replaced parts in the last 6 months:

CCV
DISA
Expansion Tank
Fuel Filter
Fuel Pump
Oil Filter housing gasket
Vanos oil hose
DME updated

I'm out of ideas. I tried unplugging the MAF and the idle seemed rougher but didn't seem as erratic. Since I have a steptronic, when I unplugged the MAF the transmission went into limp home mode so I could not really drive it and get a good feel for it.

I don't want to drop money for a new MAF without being confident that this is the problem.

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Old 03-22-2011, 11:39 PM   #2
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Well, MAF stands for Mother-of-All-Fking-problem..Why don't you try local BMW shop, swap the MAF and monitor the result? That'll save you some money and reduce your stress
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Old 03-22-2011, 11:43 PM   #3
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Maybe you should try cleaning it before you buy a new one.
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Old 03-22-2011, 11:46 PM   #4
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^NOOOOOOOOOOOOOOO failing MAF will fail anyway, cleaning MAF is only part of a maintenance!
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Old 03-23-2011, 04:52 AM   #5
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Quote:
Originally Posted by 28firefighter View Post
So after having my fuel pump and filter replaced, I'm still having issues. What I initially thought was unrelated all seems to be adding up to what I think is a bad MAF.

Here are my symptoms:
Erratic idle and idle dipping

Sluggish acceleration

Slight...skip...in 4th gear between 1500 and 2000 rpm.

Engine bogging between 2k and 2500 rpm when at higher speeds or trying to get there.

The car has no codes lighting up or pending. It has no vacuum leaks either. Here is a list of replaced parts in the last 6 months:

CCV
DISA
Expansion Tank
Fuel Filter
Fuel Pump
Oil Filter housing gasket
Vanos oil hose
DME updated

I'm out of ideas. I tried unplugging the MAF and the idle seemed rougher but didn't seem as erratic. Since I have a steptronic, when I unplugged the MAF the transmission went into limp home mode so I could not really drive it and get a good feel for it.

I don't want to drop money for a new MAF without being confident that this is the problem.

Sent from my SPH-D700 using Bimmer App
No vacuum leaks? You removed the lower intake boot to check it? If you have mileage on car and haven't done this, it's the presumptive winner!

If maf is bad, then disconnecting it should make the car run smoother, or it usually does. A large intake leak, though, often varies, as the crack lets in varying amounts of unmetered air at different times.

And, the surging might be this, or might be the stuff most do when changing intake boot...cleaning maf, disa, icv, tb, and replacing rubber stuff behind as appropriate.
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Old 03-23-2011, 08:44 AM   #6
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Thank you all for responding. All the rubber pieces have been checked and the car has been smoke tested more times than I'd like to think about.

The DISA is new and functioning and the ICV and throttle body are both clean and functioning properly. Thus all I could come up with was the MAF.

The idle issues seemed to clear up when it was unplugged but it is hard to tell for sure since it was really random when it happened. The limp home mode really made it so I couldn't do very much in terms of testing it.

Last question: I came across an aftermarket replacement for about $99. Would getting this be a huge mistake?

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Old 03-23-2011, 09:04 AM   #7
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Quote:
Originally Posted by 28firefighter View Post
Thank you all for responding. All the rubber pieces have been checked and the car has been smoke tested more times than I'd like to think about.

The DISA is new and functioning and the ICV and throttle body are both clean and functioning properly. Thus all I could come up with was the MAF.

The idle issues seemed to clear up when it was unplugged but it is hard to tell for sure since it was really random when it happened. The limp home mode really made it so I couldn't do very much in terms of testing it.

Last question: I came across an aftermarket replacement for about $99. Would getting this be a huge mistake?

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Most will say yes, a mistake. I'll just say that I read here that they fail all the time as do most aftermarket electric things!

You cleaned it with maf cleaner very, very well...didn't touch it, treated it like eggs...cleaned electrical connections?

I don't know what you know....just asking.

DME updated how recently, by whom? What issue prompted that, if any?

From here on, OP, I'd just be guessing...and doubt it's a fuse or battery, though it's always nice to cover all basics first!

GL!

Doug
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Old 03-23-2011, 09:06 AM   #8
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Quote:
Originally Posted by 28firefighter View Post
Last question: I came across an aftermarket replacement for about $99. Would getting this be a huge mistake?


Yes, mistake.

Buy a Genuine BMW MAF.
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Old 03-23-2011, 09:14 AM   #9
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Check your plugs lately?
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Old 03-23-2011, 01:46 PM   #10
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I have not cleaned the MAF because the general sense I get here is that it is a complete waste of time. I can give it a shot, and let you folks know. I park outside and its pouring rain for the next few days so it'll have to wait, but as soon as I do I'll report back.

Spark plugs are new as of when I bought the car (had the dealer do it), and the battery was replaced by the previous owner within the last 2 years so I doubt its that.

Thanks all!
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Old 03-23-2011, 02:05 PM   #11
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Quote:
Originally Posted by 28firefighter View Post
I have not cleaned the MAF because the general sense I get here is that it is a complete waste of time. I can give it a shot, and let you folks know. I park outside and its pouring rain for the next few days so it'll have to wait, but as soon as I do I'll report back.

Spark plugs are new as of when I bought the car (had the dealer do it), and the battery was replaced by the previous owner within the last 2 years so I doubt its that.

Thanks all!
I think we're all pretty much in favor of trying a $5/10 min. job to save $300.

Any shop would just replace it. Many have cleared things up, especially if they've got or used an oiled air filter. I cleaned mine with a whole can over a half an hour or so, and let it dry thoroughly, and sprayed electrical connections coz I do that a lot!

Hyundai maf might not work for you, but search that...if you need a maf.

I'm sorry, but with all the cleaning and stuff you did down to the throttle body, I'm thinking maybe another connection between lower and upper? Who did the checking on the lower tube? And you might not pick up a crack there unless trying to find it...and smoke testing it (spraying carb cleaner from the outside of the tube, might not do much at all with the way these cracks present themselves. They're sealed at idle and open up and wobble back and forth when revving...if small enough, I guess the car eventually figures it out.

Sorry, I'm persistent just coz I know half this place or better are young people who don't know anything and whose brain hasn't fully developed--I come across as dense, but I'm just pushing for an extra look.

The lower boot can get connected but not really be...tube/tubes running into upper intake, sorry if I'm repeating...I say the same things a lot! If you're not a mechanic and doing stuff you can miss simple stuff like plugs. If you are a mechanic, you can miss simple stuff too!

We good?
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Old 04-01-2011, 10:26 PM   #12
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Update:

I cleaned the MAF, unplugged the battery, and drove around with zero improvement whatsoever. I ended up buying a MAF and I installed it this evening, although I am out of town it was not as methodical as I would have liked. After a 4 mile test drive including a little highway, here is what I can tell: Low end power seems a little more consistant and the skip in 4th gear seems to be gone. The bogging is improved, but not gone - I'm wondering if 4 miles of driving just was not enough to reset the computer oxygen/fuel readings. Idle seemed smoother, though still had some of the dips albeit not as rough.

I'm hoping this resolved it but will let you know. I can't unplug the battery right now because it is parked outside for the night, but I assume the more I drive it the better.

A family member suggested a fuel injector service (cleaning the injectors and then running a thing of techron through it) but I'm skeptical. Any thoughts?
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Old 04-02-2011, 05:58 AM   #13
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Quote:
Originally Posted by 28firefighter View Post
Update:

I cleaned the MAF, unplugged the battery, and drove around with zero improvement whatsoever. I ended up buying a MAF and I installed it this evening, although I am out of town it was not as methodical as I would have liked. After a 4 mile test drive including a little highway, here is what I can tell: Low end power seems a little more consistant and the skip in 4th gear seems to be gone. The bogging is improved, but not gone - I'm wondering if 4 miles of driving just was not enough to reset the computer oxygen/fuel readings. Idle seemed smoother, though still had some of the dips albeit not as rough.

I'm hoping this resolved it but will let you know. I can't unplug the battery right now because it is parked outside for the night, but I assume the more I drive it the better.

A family member suggested a fuel injector service (cleaning the injectors and then running a thing of techron through it) but I'm skeptical. Any thoughts?
You might be right about the car taking a while to realize it has a new MAF...you disconnected the battery before installing?

I use Techron 3-4x/year. Never had injectors cleaned otherwise...Techron works nicely for me.

The one thing I don't see in your list is the lower intake boot...it's an elusive bugger and many skip over it because they don't see a tear, or a tear doesn't 'show' on smoke tests...but if you haven't removed it and physically checked the elbow on the lower boot, I'd say do that if Techron doesn't magically make your car all better. I know you said you checked all the rubber...but I don't know how you did that...just being obnoxiously persistent about this common boot tear. I don't know your mileage, but with all going on, seems like it's time for that boot to tear!
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Old 04-05-2011, 08:42 PM   #14
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Just another update after the MAF has had some time to adapt. My car is at, about, 95% I'd say. It still has some slight bog but it is barely noticeable. I will likely run a thing of techron through it anyway come next fill up. The biggest difference is the gas mileage - I'm probably getting 4-5mpg higher than I was before, which is great. As an aside, I removed the lower intake boot and check it out, and it was fine.

Anyway, thanks for all the great advice here.
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Old 04-07-2011, 12:07 PM   #15
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After a 300 mile drive last night, the car is bogging still at highway speeds and my idle is still dipping quite a bit. My low end power is back and great, so I attribute that to the MAF.

Assuming no Vacuum Leaks, what else could be causing this bogging and perhaps idle issues?
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Old 04-15-2011, 01:43 PM   #16
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Bump to this.
similar problem: my car still throwing out fault codes related to the MAF (short circuit), i've recently changed the Maf with a NOT OEM one and changed all the pipes that goes behind that (from maf to t.b. due to some cracks)

but I still have some problems:
smell of gasoline and some small bangs from exhaust when shifting(sexy,cool but not normal)
car pulls 'till 5500-6000rpms then literally dies (like limiter)
if i release the gas pedal from full throttle around 3000 rpms it kicks back (hard to explain,decelerating is not smooth as usual)
higher fuel consumption..

i've noticed that the engine light comes out only if i drive on highway on long distance....

any ideas??
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Old 04-15-2011, 03:02 PM   #17
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I've found this:

POOR IDLE - e.g idle speeds sometimes drops down to 500 as well as being unstable.

HESITATION - often there's a delay before it accelerates

POOR PERFORMANCE e.g engine slow to rev, especially below 2500rpm

The cause is bad/corroded connections at the rail pressure sensor and ecu terminals. Requires new harness no YMQ503320, SENSOR STC4768, O RING MYX000040. The harness replaces the existing wiring between ecu and sensor. One owner had the above problems and initially suspected the maf sensor as the symptoms are roughly similar. A Pierburgh maf and Mafam MF75p were tried to no avail. His local Landrover dealer fitted the above parts from stock (they had lots in stock as its a common problem apparently) and this cured all the symptoms.

This is solution for 320D, so obviously you have no use of parts name and part about "rail pressure", but this sounds similar to your problem, the point being this could really be some bad connections or wire harnesses. As somebody above said, maf is mother of all fvckups, but before you change it (many drivers to that to no avail), there may be cheaper possibilities.
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Old 04-15-2011, 03:08 PM   #18
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Quote:
Originally Posted by 28firefighter View Post
Update:

I cleaned the MAF, unplugged the battery, and drove around with zero improvement whatsoever. I ended up buying a MAF and I installed it this evening, although I am out of town it was not as methodical as I would have liked. After a 4 mile test drive including a little highway, here is what I can tell: Low end power seems a little more consistant and the skip in 4th gear seems to be gone. The bogging is improved, but not gone - I'm wondering if 4 miles of driving just was not enough to reset the computer oxygen/fuel readings. Idle seemed smoother, though still had some of the dips albeit not as rough.

I'm hoping this resolved it but will let you know. I can't unplug the battery right now because it is parked outside for the night, but I assume the more I drive it the better.

A family member suggested a fuel injector service (cleaning the injectors and then running a thing of techron through it) but I'm skeptical. Any thoughts?
if it were injectors, you wouldn't have dips, but hesitation during acceleration (pretty irritating, believe me, you wouldn't be happy talking like you do that you seem to have solved something and it would probably die on you during first start in the morning.
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Old 04-15-2011, 04:20 PM   #19
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Originally Posted by 28firefighter View Post
A family member suggested a fuel injector service (cleaning the injectors and then running a thing of techron through it) but I'm skeptical. Any thoughts?
Fuel injector services do little to nothing.

Replace or have them ultra-sonically cleaned.

Use Chevron Techron 2-3 times a year or about every 4K
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Old 04-15-2011, 11:55 PM   #20
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Well, my bogging problem is still very much present after having driven about 1000 miles with the new MAF. I can reproduce this issue rapidly once at highway speeds, and no one seems to know what to do about it. The mechanics I've talked to are all split between it being a software corruption and/or some mechanical issue. We are literally out of parts to think of throwing at it.
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