Air Flow Meter Test

[TommyG]

I've got an 85 318i that fires up, but will not stay running. It starts hard, then runs for about 5secs and dies. I disconnected the lead from the air flow meter and it stays running, but very rough. Reconnecting the air flow meter kills it. Anybody know if this is a sign the air flow meter is shot?

[pettas]

Ummm.... just a guess, I am not saying this will solve all your problems, but could very well help.

Check your spark plugs, see what condition they are in.
Check your ICV (Idle Control Valve) and clean that which might be neccessary.
Check for vacuum leaks or hoses, or any cracked/old hoses. (Remember hoses detererorate from the inside out, so if there cracked on the outside, there hell on the inside)
Check your air filter to make sure it isnt clogged (Not sure if this helps)
Check your intake book for leaks

Sorry, I am not nearly the most knowledgable person with this stuff, but I am trying to do anything I can to help. Ill be sure to post back if I think of anything else.

-Andre

[TommyG]

Originally posted by pettas@Nov 29 2004, 02:19 AM
Ummm.... just a guess, I am not saying this will solve all your problems, but could very well help.

Check your spark plugs, see what condition they are in.
Check your ICV (Idle Control Valve) and clean that which might be neccessary.
Check for vacuum leaks or hoses, or any cracked/old hoses. (Remember hoses detererorate from the inside out, so if there cracked on the outside, there hell on the inside)
Check your air filter to make sure it isnt clogged (Not sure if this helps)
Check your intake book for leaks

Sorry, I am not nearly the most knowledgable person with this stuff, but I am trying to do anything I can to help. Ill be sure to post back if I think of anything else.

-Andre

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Thanks Andre-I'll check those items. I think the issue might be a bit more dramatic though since the car worked just fine at one point then after being parked for 3 days it developed this problem.

Let me know if you think of anything else.

[idanity]

maybe water in the rotor.

perhaps someone put water in your gas-tank

battery must be fully charged to run properly too.

[TommyG]

Originally posted by idanity@Dec 2 2004, 08:34 AM
maybe water in the rotor.

perhaps someone put water in your gas-tank

battery must be fully charged to run properly too.

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Water is a possibility, but I don't think I've pissed anyone off enough to put any in my tank. The batt is a few months old and fully charged.

What's the connection between the running problem and when I disconnect the Air Flow Meter? Again, when I disconnect the Air Flow Meter it starts right up, but runs very rough (obviously due to no air flow signal to regulate mixture). Once I reconnect the Air Flow Meter the car revs, then dies after 2 sec.

Can the water be setting the mixture off?

[idanity]

What's the connection between the running problem and when I disconnect the Air Flow Meter? Again, when I disconnect the Air Flow Meter it starts right up, but runs very rough (obviously due to no air flow signal to regulate mixture). Once I reconnect the Air Flow Meter the car revs, then dies after 2 sec.

Can the water be setting the mixture off? see next post for more probable cause.

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[/quote]

what does the A.F.meter look like inside>?
is it shiny
is it varnished and dark?

that will be a large boost in response when that is perfectly clean.

heres how i clean mine once a year.

remove it, is the hardest part.
1 can of AIR-INTAKE-CLEANER.
half can of BREAK CLEANER.
bunch of long swabs or skinny brush (not metal bristles)
air intake lube.

turn upside down and wear eye goggles.

use the break cleaner carefully and wet the brown spots,
use brush/swabs and repeat until swabs are clean.

then finish up with the air intake cleanser very liberally.
this leaves NO-RESIDUE and displaces other chemicals from the brake cleaners stronger agents.

i use one can a year just on that...including the manifold and all, i do it all at once, it takes about a hour with all the hoses and clamps to get done, i just replaced some hoses tooo...
my car rides much differently now, very smooth and glides into advancements too.
plus the early morning idle is much more stable too.

take pics too, i will next time i do it. itll be next sept.

[idanity]

okay the connection in between the air flow meter and your stalling is only connected if you ever had a BACKFIRE.

IN that case a backfire will (may) bend the flap in the a.f.meter and will cause incorrect resistance,
The flap will then bind or stick , jam in a altered position and hence give a major problem. albiet useally rich running car and stall when idleing:

sorry i dont focus enough yet, im in progress of bending spoons...

please photo what ya do to...
wear latex gloves and eye protection when useing liquids and pressure.

[Nealdavis4]

On top of the air flow meter, check to make sure that the black cover that protects the electronics is still siliconed around the base and is secure. I've heard of moisture getting into the electronics and causing havoc with the circuit board... Wish I could be of more help.

[APS]

sounds to me like you're on the right track
dont just disconnect the afm, pull it and the airbox right out... if it idles stable in that state, your afm is probably shot...
they're not a repairable item, get a new one... (you can pop the top and move the board with resistor track over by a smidge, but will probably damage it in the process - even if it works its only a temp fix -good proof of diag though)
testing the risistance between pins is poitless... that wont show up dead spots, only broken tracks... you can do some more usefull diags with a CRO while moving the vane
when you replace it, it should be tuned to your car (will probably be ok, but never 100% if you dont) - you need a cro on the O2 sensor (again, multimeter aint enough) and to twidlle the bypass screw on the afm untill its calibrated - you probably need an efi specialist to get it right

could be a sick O2 sensor (a shot AFM will eventually kill the O2 sensor too)

[infotron]

did you ever sort out your problem as I have exactly the same thing. Could write a dang book about what I have tried

[idanity]

well write the rough draft here and well help ya out if theres any holes in the script.

[Kowalski]

the only reason it runs rought when you disconect the wires is because the engine goes into fail safe mode, and just does rough settings for everything. so the engine runs like crap because it doesn't want to make it run at optimum performance because it can't calculate it because one of your sensors is shot. could be a temp sensor, 02 sensor, air flow meter sensor, and any other sensor these things have.

[e30fanm3]

A bad temp or o2 sensor will not make your car run rough enough to just die. i would go to a junk yard and get an air flow meter cause they hardly ever go bad. check your main relay and fuel pump relay, if they are original you need to replace them anyways