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just did a scan of the archives. Is it true that a MAT on a MAF car does nothing for fuel,idle,spark, etc.? It is just used for EGR? I don't even have EGR hooked up. Perhaps I should just leave my MAT alone if it does nothing

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Just doing a quick check of things. With the engine not running, and cold, I did a quick scan. The only thing odd was my MAT. It read 45 degrees Celius. That's roughly 120 F. Today it was a cool day at 20 degrees C (70-ish F).

I figured the engine may have to warm up and go into closed loop or something odd like that. So I let it warm up. Closed loop. Still the MAT read high.

I took the top of my TPI off to see if the wires were pinched. Nope.

I measured the resistance of the sensor and it came it at 1200 ohms. The plenum was cool to the touch. 1200 ohms according to my GM manual is right about the 45 range.


So I am just curious what problems this might cause.

Is it used the moment the engine is started? Would it cause a lean condition on cool days?

Mark.
PS. Anyone know the part number for a 1987 MAT from a 5.7L TPI?

 

MAT reads the temp of the in going air. If it is reading hotter air than is actually there, it may be running the motor lean due to hotter air not having as much O2 in it as cooler air. Less O2 means less fuel is needed. Not sure how bad this would be due to the O2 sensor should pick up the lean condition and adjust fuel to compensate. Hopefully one of the other ECM gurus will chime in as I could be off on this.

 

If it had any affect at all it wouldn't be much and only then in open loop. Once the ECM enters into closed loop the O2 sensor overrides all the other sensors output and make the final fuel metering decisions.