airflow meter issue

[mrcosmos]

Hi,car ran perfect yesterday,today like a dog.Missing below 2000rpm.Code reader says 12[airflow meter].Should any of the wires have 12v.R/B,U/G,N/U/R? Suspect the R/B should,goes to header plug by ecu with other R/Bs.Any ideas appreciated.Dave.

[blitzracing]

This is on a 1992 loom:

Red/black. Ground

Blue/Green Air flow signal- should be .2-.7 volts (no air flow). Tick over on the 3.9 is about 1.7 volts

Brown Orange +12v

Blue/red CO trim value.

Mark

[mrcosmos]

Hi Mark thanks for that,will check the brown wire in the morning for 12v[same wire feeds injectors 1-7]Cheers,Dave.

[mrcosmos]

Also is there any way of testing the airflow meter at home or is it a specialist job?Thanks.Dave.

[dnb]

You can borrow mine as a swap test if you like. It's not like I need it on the car

[mrcosmos]

Hi Dave,thanks for the offer.Will check all wiring in morning,if ok will email about borrowing.Regards,Dave.Also Dave what are the symptoms of defective meter? Mine is ticking over rough,plugs are black,smell of fuel,jumping like a kangaroo below 40 and fault reader says 12[defective meter or out of range or defective wiring].

Edited by mrcosmos on Sunday 24th August 22:13

[mrcosmos]

Also disconnected airflow meter while running and no change to engine note/tone?

[mrcosmos]

Thanks for all the help,job done.No 12v at airflowmeter plug on brown/orange[terminal pushed back].Just for reference the wire comes from Splice No7 in engine harness,splice No7 also feeds injectors 1,3,5,7.Regards,Dave.

[blitzracing]

mrcosmos said:

Also is there any way of testing the airflow meter at home or is it a specialist job?Thanks.Dave.

You can take some readings from the output with a test meter between red and black to blue and green. With the engine off, the output wire should be less than .7 volts, at tickover its about 1.7 volts, and at full power under load, its about 4.5 volts. These values are approximate, as engine size and cam will make a difference. Beyond that calibration is quite difficult, unless you have a known good one inline with the suspect one and a variable air supply, ( I used a 2.2kw garden vac' on a variable voltage supply) and compare voltages. As for the engine note change, dont forget the ECU has a fall back mode when it looses the airflow signal, so the engine keeps running.

Mark

[mrcosmos]

Cheers Mark.Car now runs sweet again.