What is the MAP sensor, and why are people 'whacking' them? How do I know if my MAP sensor needs to be whacked? How do I know if it needs to be replaced? Do you just hit it with a screwdriver handle or something? I tried a search on "MAP sensor", and nothing relevant popped up.

 

"Whack" was an affectionate term I used to describe what is done. You don't really "whack" it. You just give it a firm knuckly thump or two in case there is debris caught up in the hole. The main thing is to unclip and re-clip the wiring harness to make sure the connection is fresh and an ECU reset doesn't hurt either if all else has been tried and doesn't resolve whatever is that's ailing the car.
All this is described in detail in the FAQs.

 

and here it is
"map whack"

 

Thanks guys...I thought I had looked all through that section....now I see it though.

And thanks for the link.

 

if you were curious about what the map sensor does, it converts manifold absolute pressure into electric signals into the ecm. '=)*