Im getting an AFM thermosensor error code, my check engine light wont go off, and the ohm readings are inconsistent with the shop manuel, so i think the thermosensor is fubared. I bought the AFM off of a forum member, but id rather not start some **** if i can help it. What exactly would happen if the AFM thermosensor is not working? Is there anyway i can take it apart and replace the sensor with a sensor from an N/A AFM i have?

 

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The AFM only measures air volume flow, not mass airflow. The ECU uses the thermosensor to figure out the air density, and combines that with the airflow reading to get mass flow. Then it injects the right amount of fuel for that mass of air.

Basically if the thermosensor's not reading right it'll screw up the mixtures, because the ECU thinks the mass airflow is different to what it actually is and injects the wrong amount of fuel.

I have no idea how you'd repair it, but it might be something simple like a corroded terminal inside. Pop it open and have a look for anything obvious.

 

hmm... ill do that. But will it cause it to run rich or lean? doesnt it defualt the temp to liek 70 F or something if it is not working?

 

According to my Chilton's manual, in 88, if the AFM Intake Air Temp sensor trips a code, the ECU maintains a constant 20C (68F) ... however, I have no data on the 90s. It would have to default to something.. that's just the way ECUs work.

 

Look into the afm opening. I think you'll see a small bulb sticking up. That's it.

Like the KIWI said in another post.......on a turbo it's very important. Under boost you want it to be accurate to prevent the mixture leaning out and causing problems. Otherwise...I don't think you'll notice the difference, at least not dramatically.

The default value is in the online manual.
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Is there anyway i can swap the thermosensor from an N/A AFM to my T2 AFM? How do you take apart the afm? do you have to break it open? ive been trying to take it apart, but it seems that its glued together very well.

 

According to the FSM's, the NA and Turbo thermosensors are the same, so if you can figure out how to do it, it could work.

If there's a problem the ECU defaults to a 20degC/68degF value. If the actual air temp is higher than this, more fuel will be added than normal. If it's lower, less fuel will be added.

 

but wouldnt the other thermosensor in the TB elbow control this too?

 

I think you should go to the for sale site on this site, and try to buy the right one for your car. I'd pay no more than fifty bucks max.

But.....here's what you can do. See the black cover on the afm. Just above the electrical jack???? Get out a razor knife and cut around the edges. That's to cut off the clear rtv around it. Now get a thin screwdriver out and get under the edges and pop it off.

Now look at the bulb in the inlet and see where its located. Now look in where the black cover was. You'll see two black wires coming out of the sensor. They have quick disconnects that attach to the electrical jack.

The rest is up to how daring you are. It would seem that you can loosen the three screws that hold the plate above the sensor, along with the screws the hold the electrcal jack in place and then maybe remove the bulb/sensor.

Here's a idea. TAke that black cover off. Pull the two black wires off the electrical jack. NOW ohm out that sensor and compare the values to the fsm. I bet they are good.
I did not do that. I just looked at it with the black cover off. The black cover is that one that is about three by three and round on one end.

If you decide to take the screws out.......make a picture of the outfit prior to removal so you can get back to square one. Done.

 

Why dont you put the thermosensor in the rubber elbow that goes to to the AFM. To take the AFM apart, you need to pry the black plastic piece out of the AFM Then, if I remember correctly, you have to remove the potentiometer to get to the sensor. Good luck getting that back in without screwiing up the calibration.

^^Bet me too it.

 

Well.....I took the three screws out and the two for the jack. My advice is......don't **** with it. You'll not get back to square one and even if you do, every time in the future that your car acts up....you'll wonder if it's the afm.

 

well dammit, rotorific owes me some money then

 

No, different sensor for a different job.

 

****DelSlow******

I'd still take the black cover off and then pull both quick disconnects off the jack that come from the sensor. Then ohm ou the sensor. I bet it ohms out good and it's the connections at the jack or the quick disconnects not secure.