I think I have read almost everything there is to find on the internet about people having prblems withthere MAF and I still can't fix mine. here is the story.
it all starts when my CO% is checked and is over 10% which as we know is way too high. therefore i check all the relevent sensors like temp sensor etc. and find all of them to be working. I then check voltage at the MAF 12v+ ok and 12v- ok but airflow and CO adjustment not correct. i clean it and it doesn't help, so I buy a new one fit it and battery volts are ok, 1.7v on CO adjust but still not correct on airflow volts ( they don't change with or without engine running.) Can this be correct or have I got a duff/broken new MAF? I then check all wiring to and from the ECM and they are also ok. I believe that the 2 wires inside the MAF, one of tem should glow "hot" ..With the wiring connector on the correct way (socket on MAF and cable conection forms mating each other) there is no "hot" but I noticed my cable conector is stretched and has been put on turned 180degrees so I try this and noe the MAF is hot and glowing inside but the CO and air volts are all wrong.
Am I correct in saying the MAF should glow hot on one wire and if i gently pass air over the glow area the airflow volts should rise? this information is sent to the ECM I'm starting to pull my hair out about this one.
Basically shouldn't the MAF work regardless of other components?

any thoughts would be great...
I'm ruling out the cats at ths point (regarding te high CO) as over 10% CO is too high even before cats. Isn't it?

does anyone have a diagram of which wire goes to which spade connector on the MAF? I have all the wiring diagrams and the conector numbers are correct but which pin on te MAF should recieve the 12v+ and 12v- and the other two also. maybe someone can take a picture of theres so I can compare.

 

I wish I knew the answer on the MAF.
Lets start with the basic's, have you done a tune up?
New spark plugs and spark plug wires?
How about the dizzy cap and rotor?
How about the front oxygen sensors?
I assume the air filter is clean.

 

From the RAVE electrical manual for a 95 (assuming that your 3.9 is not same as my 97 4.0 GEMS);

Pin 2 is Red/Black - and is the ground lead switched thru the ECU.
Pin 3 is Blue/green and goes to ECU pin 35 on conector C243
Pin 6 is Blue/red and goes to ECU pin 22 on connector C243
Pin 5 is Brown/orange and goes to the engine load control relay contacts fed by Fuse F6 in underhood box, powers up the sensors and such when ignition key is switched. That is the +12 power.

I have attached connector drawing from the RAVE (under connectors, indexed by number).

All this is based on you having a 3.9 with a distributor. If no distributor, you would use the GEMS wiring diagrams.

 

thanks for that I'll have a look again tommorow.
new airfilter
other parts in fine condition. I haven't checked the type of plugs, they could be the wrong ones but I'm pressuming that they are correct as all service since 2002 has been done by a qualified autoshop. I believe one engine side has been overhauled six months ago. what about a camshaft? one tooth out or something? faulty injectors?
still doesn't fix the MAF problem... ECU?

 

What pin on the MAF goes to which? That info only tells me where they are connected at the other end. 12+ volt goes to which pin etc. that way I can be sure the connection is on the correct way.
Am I correct in saying the wire should glow with ignition?

 

No the wire inside the MAF should not glow with the key on, it gets hot but not that hot.

 

ok thanks for clearing that up...

 

Can someone reassure me that the MAF should actually work without being attached to the ECM. and if it receives 12+ and ground and air is passed over the internal measurement wires the airflow volts should rise regardless of anything else. this volt information is sent to ECM. correct?

 

The ECU does some of the math. The MAF heats to 212F in one spot (Lucas MAF) vs 350F (GEMS). With a 3.9 you have the old style, voltages and pix are attached. No matter which type of MAF you have, avoid spraying cold cleaning fluid on a hot sensor, and avoid slurping an air box full of cold snow melt creekwater whilst wading.

 

So it has to be connected to the ECU to great the volts on the pin from MAF?

What am I missing? What about crank position sensor is that relevant for the MAF to work correctly? or other sensors that I could have missed.
This is killing me me!!:-)

Thanks again for all your help.....