The guy that I paid $XXX said he replaced it but i cant find it for my life! just wondering what it is and what it does and where it is

 

Here ya go...link to my 96 factory manual...

http://www.motorcraftservice.com/pub...0/STJ3E012.HTM

 

This should be mounted on the firewall up towards the hood level, slightly offset to the passenger side - just look for a vacuum line coming from the manifold and an electrical connector, both going into the same black box.

 

To the other part of the question -

The MAP (manifold air pressure) sensor was used in the earlier days of fuel injection, now mass-air flow (MAF) is the preferred sensor due to accuracy.

Basically, to know how much fuel to inject, need to know how much air is present.

The MAP sensor measures the manifold pressure.

Yes, the manifold is under a 'vacuum', but in the scientific world, there is some amount of air present all the way down to an absolute vacuum, which is approx. 30" of mercury.

For our purposes, vacuum relates to the pressure below atmospheric conditions. The term 'pressure' relates to pressure above the absolute vacuum point. There is a 30" typical spread between atmospheric conditions and absolute vacuum (this is the barometric pressure value given on the local weather - this is what they're measuring). So, 10" vacuum is equal to 20" absolute pressure.

Anyway, probably way more than you were interested in above - when this pressure value is combined with other factors like air temperature, engine speed, and throttle position, get a reasonably fair measurement of air flow via the computer's calculations and look-up tables.

 

thanks!