what does my map sensor do

 

I am pretty sure that it senses Barametric Pressure and tells the computer how to adjust the air/gas flow properly.

 

MAP sensor stands for Manifold Absolute Pressure sensor. It measures air pressure inside the intake manifold (barometric pressure). As with any electronic sensor, the resistance through this sensor changes as the pressure changes and the PCM interprets the changes in resistance and responds accordingly by altering fuel flow and spark timing to optimize performance based on the air pressure.

 

89 351

Where is the MAP sensor. and are the hard to change, and should you get OEM and about what do they cost?

 

Unless it moved around the engine bay in earlier years the MAP sensor should be located between the heat/AC bulkhead and the passenger side of the engine up on the firewall. It will have about three wires and a vacuum line running to it. I always replace sensors of any kind with OEM units. Its cheaper in the long run to spend a little more initially and KNOW that the part is A) the right one for the vehicle and B) manufactured within the correct tolerances by the vehicle manufacturer.

 

replaced my map sensor couple weeks ago cost me bout $100 from the dealer, and it is located passenger side car by firewall. you should see a vacuum line coming from the upper intake into the sensor then there is a 3 wire connector going into the sensor. dont replace it unless you think you need to.

 

Thanks Greystreak and gimmeice3, Please read my post I just updated titled "pressing the gas makes her slow" Do you guys think this could be the MAP sensor??

 

I don't think that is your map sensor, when my map sensor went out I could hardly keep the motor running. Black smoke was pouring out the tailpipe and I had to keep my foot into it just to make it to the mechanic shop. The mechanic says when these go out the PCM defaults to Denver, Colorado altitude and if your lower than that altitude your engine is going to run way rich. Take your truck to Checker/Autozone and have them run a scanner on it, if the MAP is bad it will have stored a code.

 

wow this prblm sounds familiar to me i got a 90 351w in my bronco cammed out with mass airflow sensor conversion kit. since i put the kit in the truck has been blowing black smoke and just a few nights ago i had to keep my foot on the gas to keep the truck running. can a map sensor go bad if it is not in use bcuz with the mass air kit they make u disconnect the vaccum line and plug up the hole on the uper intake manifold. im tryin to get my truck runnin right and im at a loss and i cant think of anything that could be wrong with it until u just said that u had to keep ur foot on the gas and black smoke was coming outa ur tailpipe

 

With a massair flow conversion you don't need the MAP sensor. The MAF sensor does for you what the MAP sensor did. It measures the amount of air being sucked into the intake. If your loading up, you may have a problem with your MAF sensor.

 

It yells at me and thrusts a map in my face when it senses that I am lost and won't stop for directions. No, wait a minute, that's my girlfriend. Never mind.

 

Hey, I've got one of those too. Still haven't figured out how to DISCONNECT it! Irritating as the "door ajar" chime!

 

its brand new how could it be bad.and it came as a kit so the computer and the harness are all matched up. i also have a problem with rpms, it wont rev over 3300 after that it starts to missfire bigtime. it didnt do this until i put in the msd distributor and ignition coil, i figured it would run right when i put the mass air flow kit in. but it didnt only ran worse. i am gonna change the distributor back im ogonna put the stock one in and see if that changes anything.

 

I see you put a big cam in the motor, did you do it or someone else? What did you set the timing at after the cam was installed? Did you disconnect the "spout" connector when you timed it?

 

i put the cam in myself. set the timing at stock with the msd distributor but with the stock distributor i had to advance it. i dont really trust mechanics at all so i tend to do most the work myself