Thread: Air Flow Meter Supplier

While the “CO trim pot” not connected to the MAF's airflow electronics it is still part of the MAF body unfortunately. I recommend you go to LovemyRangie's Tutorial mentioned above to test if that potentiometer or pot is functioning.

If not then you have 2 options, replace the MAF or a cheaper option of splicing into the MAF loom end a 1000 Ohm potentiometer between wires at MAF connector 2 (wire not cut) and 6 (wire cut)or at the ECU loom end between pins 25 (wire not cut) and 22 (cut). Don’t forget to tell your mechanic!!

I note the replacement for this fixed CO trim pot function being oxygen/O2/Lambda/catalyst sensors was not supplied to the factory fuel injection systems in Australia that use these MAF’s (except there is a catalyst fuel map sitting in the ECU chip).

MAF Group Buy thread is now up at

V8 MAF TEST & GROUP BUY

Peel back MAF boot connector. You will find on underneath that each connector is numbered. To check the airflow signal backprobe ground connector 2 (red with black trace or just black) and airflow signal connector 4 (blue with green trace or just green). Switch on ignition (but not starter) and expect to see 0.30 - 0.35 volts. Switch off wait 10 seconds and then switch ignition on again. Airflow signal should immediately go to 0.30 – 0.35 volts.



Witch Maf is being tested here i am a little confused
If its a 5AM they dont have a wire for pin 4

Test Correction.

+ "Airflow signal" connector is MAF connector #3 on both 3AM and 5AM MAF's. Don't understand why I said MAF Connector #4 (which is blank)????

Gets a bit confusing with MAF ground - connectors using both #1 and #2 or only one of them depending on MAF and MAF wiring harness vintage.

Rest assured though the MAF which is the subject of the "group buy" is backwards compatible with all harness vintages.

Sounds as though I should post a testing tutorial inc pictures.

Thanks heaps

Originally Posted by steve_35

Check this guy out on ebay they are in the UK VERY CHEAP compared to here


glowplugman1

Originally Posted by cockie55

Here are some pics and test info for a hotwire MAF. The first picture shows the hotwire setup which is connected to the underside of the circuit board. The thin grey sensor in the foreground is the actual hot wire. Cleaning this with Contact Cleaner etc after it is heavily coated will probably not be successful though it might improve reading.

The second picture shows the circuit board. It is pretty simple as ItsNotWorthComplaing indicates. My view is the alloy casing on the 3AM and 5AM MAF’s while making it very robust does great things for transferring heat to these electronics and I think the reason why later MAF’s are plastic along with being cheaper to build. However as you can’t simply swap in a plastic (and larger throat) 20AM MAF from a GEMS RR without first changing the fuel map (to compensate for the different airflow to voltage ratio), we are stuck with these alloy MAF’s (or go Megasquirt etc). The only moving part is the variable resistor or “pot" seen on the right hand bottom corner of the photo and this sets the CO trim at idle. The “pot” is sending that voltage direct to the ECU and is not connected to the AFM/MAF electronics at all.

Many people confuse being able to achieve this CO adjustment with having a MAF that works??? This is not the case!!! You need to check the airflow signal from the MAF to the ECU in conjunction with a gas analyzer and preferably a dyno to see if your MAF is working OK. However as most people don’t have gas analyzer at their disposal and 4 wheel dyno time is expensive (and not necessarily in the hands of those who understand Rovers), you can still tell a lot about you MAF by the airflow signal output.

As most people don’t have an oscilloscope lying around a digital multi meter (preferably one that has a manual/auto range single digit DC voltages) is OK.

Peel back MAF boot connector. You will find on underneath that each connector is numbered. To check the airflow signal backprobe ground connector 2 (red with black trace or just black) and airflow signal connector 4 (blue with green trace or just green). Switch on ignition (but not starter) and expect to see 0.30 - 0.35 volts. Switch off wait 10 seconds and then switch ignition on again. Airflow signal should immediately go to 0.30 – 0.35 volts.

If it goes above this say to 0.5 - 0.8 volts and takes a few seconds to drop down to 0.30 - 0.35 volts this is a good sign a Rover hotwire MAF is on the way out or already defective. A defective MAF may also be producing at slow idle an airflow signal in excess of 2.0 volt instead of around 1.7 volts for a 3.9. The faulty airflow signal does not necessarily mean the ECU will trigger a fault code / go to limp home mode but more probably be picking a fuel map for a moderate load when it does not need it. This will equate to lousy fuel consumption.

By the way if you find your CO idle trim is set lean or down to around say 0.1 volts instead of around 1.4 volts (for non cat) someone may have set this to compensate for MAF setting a richer signal to the ECU. Note: Connectors 2 and 6 (or outside connectors) measure CO trim voltage and Connector 2 and 5 is 12v/battery supply voltage to the MAF. If you have an additional earth at connector 1 (or outside closest aircleaner), you probably have a harness from the MAF changeover period.

This test is a bit off my post topic however I will mention it in a “MAF Bulk Buy” post I hope to put up this weekend.

Thanks for the info, it is a great help, however you refer to connector 4, this is blanked out on my 5am AFM, Im I missing somthing?

All 5AM MAFS are made in China. Don't believe the bull, some overseas sellers are claiming theirs is made in Brazil or their "own Factory"
There big profits to be made on the cheap Chinese copies. They buy them for peanuts , thus can sell them at ridiculously low prices.
We were importing them a few years ago selling them mostly without problems, then the head ache started with some failed units. So we don't deal with them. Also when things go sour, you'll find paying for return post of item and trying to get your money back is a drawn out process.
Bargain are some times NOT bargains.
Caveat_emptor

I recently purchased a brand new Bosch MAF for my 1987 Classic made in France for $365. These are the vane type + very complicated + difficult to get. Contact Logicar in Vic. Ph-03-98737009 . They were very helpful + well priced . They also recondition units for about $200.