how do you tell your MAT sensor is bad (also, where would it be located on a 86 2.8 mpfi) and can you tell if its fried in another way than the ol' auto zone diagnose thanks fellas, really apriciate advise on this one

 

MAT sensor? I've never heard of one, but hey, I learn something new every day... Do you mean MAP or MAF sensor?

 

Manifold Air Temperature sensor

 

Hmmmmm... I'm familiar with the IAT (intake air temp), but not the MAT.

There are sensors located to the rear of the lower intake manifold. That may be one of them. As far as testing goes, most temperature sensors vary resistance with temperature.

You might be able to meter it with a DMM, and using a thermometer and the MAT sensor chart for temp/resistance, you can determine if it is functional and within specification.

 

well MAT is what the fella said at AZ, what is the sensor located in the factory air can there right behind the airfilter?

 

IAT = MAT, same part, different names. Its the little screw in sensor in your air can. Mine's hangin because of my "import" style filter instead of the crappy can.

 

ok yeah, that helps alot, now can ya tell me how to see if its toast, other that the diagnose test????? also, what would a bad MAT/IAT cause, (hesitation? bad acceleration?) thanks again fellas

 

I had it go bad on my Iron Duke Grand Am. The car ran like crap when it was cold. Try no accelleration or any power whatsoever. Not like the Duke has much to begin with.

 

lol..MAT/IAT failure is not common at all I'd say. Never heard of one going bad personally, but it happens. I wanted to see how strong of an effect it has on the system, so I disconnected it. Car idled just fine. I stomped the pedal....ohhhhh myyyy goddddd. 5 mph, 10 mph, 15 mph, 16 mph, 17 mph, 18 mph... Felt like I was driving a Cadillac with a Geo Metro motor swapped in.

 

THANKS FELLAS, I PICKED ONE UP AT NAPPA FOR 29 BUCKS, STILL NOT 100%, AND STILL GETTING ENGINE LIGHT, BUT DID MAKE A DIFFERENCE, THANKS FOR THE ADVISE

 

The '86 GM Service Manual calls it a MAT, Manifold Air Temp. I believe GM called it the MAT for the 82-92 run; and IAT is 4th gen f-body terminology.

The MAT used to be -in- the manifold. Obviously, this was bad, because as the manifold heated up, so did the body of the sensor, throwing off the "actual" temperature of the air. So the MAT got moved off into the intake ducting. And then, it's not really a manifold air temp sensor anymore, since it's not in the manifold. I continue to call it "MAT" because that's what GM calls it for an '86... and I have an '86. If I was talking about my fiance's 4th gen Camaro, I'd call it an IAT.

ANYWAY, As to the problem; did you ever pull the code from the computer? If the MAT was bad, and you replaced it, the code should've disappeared. I'm thinking the MAT wasn't the problem to begin with...

 

And if the code you pulled IS for the MAT, reset the ECM. I'd bet a fiver that the code will go away. ANY time you swap a sensor out, you should reset the ECM. In my experience, if you don't do this, the ECM becomes confused and either throws the same check engine light, or throws codes for other sensors that make no sense. My car ran 'weird' and kept throwing MAT sensor codes after I replaced my O2 sensor. When I reset the ECM after, the car returned to normal operation, feeling much smoother of course from the new sensor, and the mysterious MAT sensor code never returned.

 

well if the MAT wasnt the problem, what would be? and how do you reset the ECM? just by undoing to batt.? cuz i did that, still get the SERV. ENGINE SOON, thanks guys, this is helping me out, and saving me time and money

 

I've always reset the ECM via the battery...that's the cheapo way without knowing which fuse to pull. Now, have you pulled the code again with the SES light when it comes up again? Are you sure it's still throwing the MAT sensor code? Maybe it's a different code now.... A simple stupid way I tell if the ECM has really been reset or not is..when I go to start the car. In 90% of cases for me it will stall on the first start. If it doesnt stall, it stumbles real bad for a second. That's the computer having fun with the IAC valve for a second, so it can make sure that it can control the valve, and learning which is open and which is closed.