Earlier today, I had the air cleaner assembly off of my 86 V-6 while I sprayed intake cleaner into the throttle body. I let the car idle as I was doing this, so I could get the intake clean and "flushed" out. Anyway, with the MAT sensor unplugged, the car obviously gave me a check engine light.

Still, it seemed to run/idle better without this sensor. I don't think it idled as smoothly once it was back together, though the car was much warmer at this point and the ECM may have been doing its "magic."

If the MAT was bad, how would it be behaving?

At the very least, the MAT is used to fine tune the F/A mix based on intake air temp.

I don't know how picky the V6 is but I can tell you that if it's bad on the 87+ L4 you'll get weird problems including hard to figure out ECM errors. Weird stuff like a rich or lean error but only under certain weather conditions at idle.

If you think the sensor is shot then just get another one and reset the ECM. (If you didn't already... You need to reset the ECM after any error condition is fixed.)

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11-Sept-01, The day the world as we knew it ended.

If you had a bad MAT sensor.......you would have already had a code in the ecm before you disconnected it. They are quite quick to set a code. So if you get no code with it plugged up.....i'd consider it okay. Good luck.

Phil

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GTDude
OVER 25 years GM experience

Generally speaking, if the MAT isn't working too well (and it does happen) expect loss of power as being the main symptom... If the mat reads the air temp too high, it'll back off the timing, and run it a little lean.

quote Originally posted by IRSCISA: Earlier today, I had the air cleaner assembly off of my 86 V-6 while I sprayed intake cleaner into the throttle body. I let the car idle as I was doing this, so I could get the intake clean and "flushed" out. Anyway, with the MAT sensor unplugged, the car obviously gave me a check engine light. Still, it seemed to run/idle better without this sensor. I don't think it idled as smoothly once it was back together, though the car was much warmer at this point and the ECM may have been doing its "magic." If the MAT was bad, how would it be behaving?

on my V6 all I noticed was the SES light going on and off ( 5 minute cycles)...but after I replaced it I didn't notice anything difference except that the light stayed off... ( I think / agree that it is for fine tuning and not so much for power)
But in reading your post it sounds like you are saying that it ran smoother without the air filter assembly hooked up to the TB, and after you reassembled it you noticed that it ran a little rougher..I have found that to be true in all engines that I have tried that on ..but who knows....PC