Air flow sensor stuffing up!? :(

[pche059]

Hey guys,
Was wondering if anyone has seen/heard anything like this one?
My air flow sensor gives VERY Unaccurate readings, only when the trasmition is in D!?
it's so unaccurate (so times fluctuate between 1V- 6V!?) that it often stalls the engine or make the engine rev VERY unsmoothly
but all these only happen when the trasmition is in D 2 or 1 ( only in forward gears)
it revs very smoothly when it's a P N or even R, and of coz stalling doesn't happen in P N or R,
but whenever it is in D 2 or 1 the airflow sensor reading is completely out!?

At the start i thought it was my Apexi SAFC that's faulty,
so I unplugged it and get it back with the original settings
but it didn't change a thing

I am guessing that it's the airflow sensor that's dying? (but won't this affect the reving and idling when the engine is in neutral as well?)

or i might have stuffed up my Automatic transmition computer?

any input will be much appreciated
thanks in advance

[T4 Primera]

Patrick, is your car stalling at idle when you put it in a forward gear but ok once you get going? Or is it rough all the time? Any check engine lights?

[pche059]

is your car stalling at idle when you put it in a forward gear but ok once you get going

Sandy: yes you are right, it's only stalling at idle when i put it in a forward gear but ok once the car is moving
it's fine when it's idling at reverse or neutral

Or is it rough all the time? Any check engine lights?

no it's not rough at all in neutral or reverse
no engine check lights went on

However I thought MAF should only have a voltage range between 0-5v?
according to my multi meter the MAF has given some signal over 9V at times!?

[T4 Primera]

Did this problem begin shortly after making any changes to the car?

Just guessing at some things to look for:-

Do any of the wires for your AFC run close to the shifter or shifter cable? If so, there could be a short there.

Check out your MAF wiring/harnesses for anything untoward.

With the car idling in Park, grab the MAF/AFC harnesses/wiring at various points and move it around some to see if the engine will stall. If it does then it could help you track down a wiring fault.

Was ALL your AFC wiring removed when you tried that? or just some of it.

I'm thinking you have an electrical fault that occurs in foward gears because of either the shifter cable moving (and in turn moving the wires) or because of the engine torqueing over backwards slightly and moving the wires.

Check fuses, especially the one for the auto computer if there is one.

While you have your multimeter out, check the MAF ground resistance.

Unlikely but just have a look inside the sensor hole in the MAF and see if there is any dirt or whatever in there.

Don't forget to watch the WRC on channel 3 tonite!!

[pche059]

Do any of the wires for your AFC run close to the shifter or shifter cable? If so, there could be a short there.

the wires for the afc run directly next to and below the shifter as the man ecu is below the shifter as well.

Shifter cable? which one is that and where is it? does it just go from the automatic computer to the main ecu? I do have a feeling it is something along these lines.

With the car idling in Park, grab the MAF/AFC harnesses/wiring at various points and move it around some to see if the engine will stall. If it does then it could help you track down a wiring fault.

Have done that, the engine doesn't stall, guess the airflow sensor (MAF) itself is fine, just some external factors which is changing it's reading (and only in forward gears?)

Was ALL your AFC wiring removed when you tried that? or just some of it.

No, only removed the MAF signal in and out of the AFC, and had them connected straight thru. This way the AFC will not be able to adjust the airflow reading yet change the A/F ratio


Does anyone here have any comments or suggestion about this?

[pche059]

I was moving the MAF wiring (not the actual sensor but the wire ) around all I did find a point that when I move it it does affect the engine rev and it did stall it few times.
I then went back to look at the multi meter when i was driving again, it seems like that cable is shorting out with my throttle sensor or something?
what are the possible wires that the MAF wire could be in contact with?

[95flG20]

i am having the same problem right now, the rough idle in neutral and the stalling out. i have narrowed it down to the IACV (idle air control valve) which basicly dose exactually what it sounds. if the valve is messed up then the car has no idea what to idle at, trys to compinsate then stalls.