Question about MAP Sensor

[chargerrt]

This is probably the wrong section for this question, but I only want a quick answer 

Yesterday the MAP sensor on my dad's pickup truck went out on me and when I was changing it out I noticed that it has a vaccuum hose running to it.  Why does it have a vaccuum hose?  Isn't it just an electrical part?  Some one please explain...

Thanks

Chad

[71charger_fan]

No, it senses manifold pressure through the hose and converts that to an electrical signal to the computer.

[chargerrt]

Thanks alot!  I really appreciate it!

[71_Charger_R/T]

Yep! That's what the M.A.P. stands for = Manifold Absolute Pressure

[Chatt69chgr]

And it'a not an insignificant part of the emission system.  Failure of the MAP sensor can cause an overrich mixture which can cause failure of the converter due to slagging.  The converter tries to burn the extra fuel continuously and gets so hot it melts down. 

[chargerrt]

Wow.  You guys are awesome!  Thanks a ton.  The truck would run fine until it got warm and then it would start sputtering and cutting off on me while going down the road.  If and when it ever cut off it took FOREVER for the truck to even crank back up.  Luckily it broke down in the parking lot of my apartment complex.  At first I thought that it might be water in the gas, a clogged fuel filter, or a fuel pump failure, but luckily it was only this!  Once again, THANKS!

Chad

[chargerrt]

And it'a not an insignificant part of the emission system.  Failure of the MAP sensor can cause an overrich mixture which can cause failure of the converter due to slagging.  The converter tries to burn the extra fuel continuously and gets so hot it melts down. 

That might explain why the inside of the tailpipes are black as soot

[Chatt69chgr]

If you have an oxygen sensor ahead of the converter, you can remove it and make up a screw-in connector to connect a rubber hose to a pressure gauge.  You shouldn't read more than about a half-pound to a pound of pressure.   If you see more, then the converter is plugged.  If you don't have a convenient bung like this, then you can go to any muffler shop and they will drill a little hole in the exhaust pipe and slip a little hose connector attachment to this and connect to their pressure guage and do the same thing.  They will usually do this for free.  They just tack weld the hole shut after making the measurement.  I am seriously considering welding a bung in the exhaust of my 69 charger to put a oxygen sensor in so I can use it to more accurately measure air/fuel ratio while adjusting the carb.