I unplugged mine just for kicks....and there was no change. Engine ran the same, trans shifted the same (bad) and truck drove the same. Only thing it did was turn on the CEL. So whats it do?

 

gives your ECU your intake manifold pressure to mix fuel and air properly.
Mitch

 

So if I unplug it, shouldn't the engine run different?

 

MAP = Manifold Absolute Pressure sensor. As the name implies, it measures the pressure in the intake. Tells the PCM how much fuel to give the engine. If you unplugged it and there was no difference then you might have a problem. When the PCm sees the MAP is bad or unplugged it will resort to a preset fuel table stored in the PCM. The engine won't fall flat on it's face but It should be pretty doggy though. Look for pin holes in the small rubber line going to it or boost leaks else where.

 

Thanks for the advice! I'll check it this weekend. Engine has always been kinda sluggish, thought it was normal.

 

mohare7 how is going your MPG,? because I have read that if the MAP sensor is wrong the MPG drops. Im going to check mine ASAP.

 

My mileage is about 17 mpg, unloaded, and I have a really light foot.

 

could anybody point me in the right direction/have any pics of the map sensor?

 

Icebox- it's mounted on a bracket over by the heater core on the pass. side of the engine- has a 3-wire electrical plug and a rubber hose running to it. If you have a boost gauge, you probably tapped the rubber line for your boost gauge fitting.

 

Center of the pic is a regulator for the MAP sensor. Follow the hose to the left. gray sensor is the MAP

 

TJ,

Is that an OEM regulator or are you tricking the MAP for some reason?

 

Tricking the MAP sensor. Not all OBS truck do this but my truck was defueling. It felt like a gasser hitting the rev limiter and would happen at around 30-33 psi boost (peak boost for me). Doesn't set a CEL or code like the Superduties but for $25 got the regulator and fittings and set it to 25 psi and no more defueling on the top end.

What happens is the MAP sensor isn't designed for those boost numbers so it signal gets messed up and the PCM doesn't know what to do with it. So we trick the MAP sensor and move on.

 

So, does the regulator set a constant 25 PSI or allow a maximum of 25 PSI to be seen by the MAP?

 

MAX of 25. Actually I just looked at my webshot write and I said 20 PSI there. Now I am not really sure what its set at! I need to take it off and check one of these days.

 

My rig is not modified like yours. I imagine adding this regulator to my rig is not necessary at this time, right? What is causing your engine to defuel? Is it the high boost levels?

With my stock engine, I should see a maximum of what PSI boost?

Sorry for the questions.