Air flow meter

[Jzza4]

Received a used AFM from ebay, destroyed it taking it apart attempting to clean it. It does not look like any of the air flow meters used in past threads I researched. How do I know mine is not working properly? I am trying to avoid paying over $300 for a new meter. Car hesitates around 3K rpm's untill I step on the gas or reduce speed. Could it be the idle control valve?

I am an idiot when it comes to cars (thought I was the smartest person alive after changing my own oil and spark plugs)!

Back to ebay to look for another one in the meantime.

P.S. Any good chrome wheel cleaner products anyone can recommend?

[genphreak]

Use the search button 'air flow meter' and 'afm' you will be surprised. Use carburettor cleaner, but not on bearings or plastic or rubber- ever. just metal. And don't breathe it in or get it on your hands. Be smart before opening an AFM, research it first so you know what to do nad what can break. We'll let you off since you say you don't know what you are doing - cos if you did, you'd have searched already! You also need a mini bag of silica-gel (desicant)and a tube of silicone to seal it back up. :) Nick

[joshua43214]

Some pics or a better desription of what have and what you got from ebay would help.

You car does not have an Air Flow Meter(AFM), it has a Mass Air Flow Sensor(MAF). The AFM is a lrage boxy thing with a flap inside, the MAF is like a tube with a square box on top. The MAF is a non servicable part and should not be disassembled, you can clean it by spraying MAF safe carb cleaner through it.

The basic difference in operation is that the AFM measure airflow into the engine, the more airflow the more the flap opens. The MAF measures the density of the air entering the engine. It has a wire that is heated to a certain temperature, the DME then measures the amount of current required to maintain that temp as the air flows over it and cools it.

A faulty MAF could cause what you describe, but will often cause other problems as well.

The Idle Control Valve is used at idle and will not cause hesitation off idle.

You really have 3 choices, you can take it to a shop for diagnosis, study hard fuel injection systems and attempt to diagnose yourself, or make guesses as to the cause of the problem and keep throwing parts at the car until its fixed.

Throwing parts at the car is usualy the most expensive method of diagnosis.

If you want to attempt diagnosis, give us a list of all of its drivability problems even if they seem unrelated to this complaint. folks can then chime in with suggestions on how to test parts so you wont waste any more money.

[Jzza4]

I would spray the cleaner on the part inside the round black housing? The MAf I purchased is the one on the OEM.com site which is $300+. The tube part # is 0 280 217 502 1 747 155, the part inside of it was # 369 24 2 A 510.

As mentioned before, the car hesitates when near the 3000 rpm range, but stops if I continue to press the gas or release it. Other than that, the car is fine in regards to acceleration.

Most of the threads I researched did not have pics of a 1995 525i, or referred to other car MAF maintenance.

Thanks again everyone for your replies.

[joshua43214]

Have you pulled codes yet? follow the instructions here to pull the codes http://www.bmwe34.net/e34main/trouble/engine_codes.htm keep in mind that a code only means that system is affected, not that the part is bad.

Does being in a different gear make a difference? I would suspect a faulty TPS before the MAF, since a bad MAF will usualy cause idle problems or problems on sudden accel or at more than one place. Try to see if changing the engine load makes a difference,3k rpm on incline, in a different gear etc. It is unusual for something to fail at a fixed rpm rather than a fixed load, Possible you even have a CPS that flakes out at that RPM. Do you notice the tach vibrating or bouncing when you experience the hesitation? There are numerouse things that can cause a problem of this nature, having only one symptom makes it harder to narrow down.

Do you have a multimeter and can you use it? You will need one probably to diagnose problems.

And yes, you would spray cleaner into the tube to clean it.

[Jzza4]

Joshua:

I don't have a multimeter, but the tach does go up and down in connection with the hesitation. I haven't tried driving in different gears yet, but regardless of speed, the car hesitates round 3000 rpm.

I have not pulled codes, but I'll try and post results.

[fkong777]

Does your check engine light stays on? if it does do the stomp procedure. You will get a 1215 code if it is the MAF.

I had the code and changing the MAF fixed everything.

Just a couple of other things to look at if there is no codes..
1. Did you wash the engine recently? if so maybe water in the spark plug channel.

2. Did you check all the vacuum hose for dry breakage?

3. Intake elbow can crack at the accordian folds...

[Jzza4]

I apologize for my stupidity, but can you point out these vacuum hoses on the realoem.com site?

Edit: The hesitation feels like it occurs only during third gear (only hesitates when I want to accelerate).

I was able to do the car code display procedure which came up with no fault codes. However, every time after doing the car code display procedure, the engine idles in park above 1000 (about 1250). Other start ups result in the engine idling under 1000 (about 750). What gives?

[Jzza4]

The hesitation seems to occur when highway driving. I noticed once before, stopping after highway driving, the car felt as if it were going to stall. The car also hesitated today on the highway in the 4-4,5K rpm range, after the usuall 3K hesitation.

When doing the car code display, I received the following info:

8361730
code NR 0000
K-Zahl 7296
GK82313

I was unable to get the stomp test to work.

After doing the car code display test, the car would idle above 1K rpm. Start-ups after resulted in idle under 1K.

[joshua43214]

Things get a bit difficult here since you do not have a multi meter. This is made harder since there seems to be a general assumption that the problem is electronic in nature and not mechanical. There are still many things that could cause your symptoms, but judging by what oyu have said so far, I would suspect the following parts in this order
Throttle Position Sensor. Side of throttle body
MAF
Crank Position Sensor. Front of engine,above crank pulley
Cam Position Sensor. Left side of head.

It could easily be none of the above as well. Do as Fkong suggested, with the engine running, poke arround under the hood, look for any loose hoses, There is a large hose that makes a 90 degree bend from the MAF to the intake, grab it and pull and push on it and see if the engine changes. These crack on their length or the clamps come loose causing intermittant running problems. Jiggle wires, especialy the ones that go to sensors and look for running changes. Lightly tap on the TPS and the cam sensor, try to tap on the crank sensor with a long screwdriver if you feel you can safely reach it. Often sensors with intermitant problems will be shock sensitive, so you may get lucky.

It may be worth paying someone to diagnose it since you lack the tools and the knowledge yourself. If you do this, make sure you get a clear explanation of what they say is wrong, and let us know.

You may even be able to get all of the parts I suspect for under $300.00 used, if you do this, replace them 1 at a time until the problem(hopefuly) goes away. then you can save for a new replacement part. But having a trouble code, really narrows things alot, it is normaly worth the money to have one pulled, especialy if the problem turns out mechanical.

Maybe spend some money on a cheap high impedance multimeter at Radio Shack, it wont be super accurate or drop proof, but it will be able to do resistence checks just fine. You seem to be the smart type, I am sure you can puzzle out how to use it easily enough and it will pay for itself many times over if you can do your own diagnosis on simple things.

[Jzza4]

Thanks again everyone for the replies.

Today, my car nearly stalled when I stopped at a light. This has occurred once before when getting off the highway, my car nearly stalled when stopping. Any ideas?

I looked at my MAF, which looked clean. When I bought the car, the valve cover gasket needed to be replaced, which seemed to be the reason there was some oil in the air filter housing. I Cleaned the plastic hose connecting the MAF to the throttle(?). I tried running the engine witout the sensor connected, which didn't make much of a difference.

Idle control valve, crankshaft position sensor, camshaft position sensor are next on the list

[Jzza4]

The stomp test resulted in code 1215 (MAF).

Should I try cleaning it with carb cleaner before buying a new unit? Must I remove the MAF when using the cleaner? or do I open the air filter and spray inside to the MAF?


Chrome wheel cleaner products....Anyone?

[joshua43214]

Remove it to clean it. make sure your air filter has no holes or tears in it while you are in there.

[Derek A.]

I would probably guess that your throttle position sensor has a flat spot in it. If it happens only on the freeway - I would guess a lot of highway miles with steady pedal pressure.

You would really need to look at the data stream off the MAF to determine if it was good or not. This is where a shop with spares and diagnostic equipment comes in real handy.