got a 1987 F-150 with the 300 6cyl. 4X4 ... when i first start it up it will idle fine for a few seconds and then die ... the only way i can keep it running is to unplug the air line to the Mass Air Flow Sensor ... it stays running and is actually driveable but runs rough and i have to ease into the accelerator or it just bogs down ... also has no power, terrible exhaust fumes, and gets about 8mpg ... if i plug the air line back into the MAFS while it's running it dies and then won't start back up unless i unplug it ... i replaced the MAFS a while back and it didn't make a difference ... i pulled the IAC valve off and cleaned it ... not sure what to check next??? was thinking maybe the EGR valve or a vacuum leak somewhere ... any ideas would be much appreciated

 

Your vehicle's computer should be able to provide some information. If you can get to a parts store, have them scan the computer for stored codes.

Welcome to the forum!

 

Just a quick question for you........

If you get in the truck and turn the key to the "on" position (not start), does the fuel pump(s) whine for 1-2 seconds then stop ???

That tidbit of information would be helpful..........

Oh, and are you sure you have a "Mass Air Flow Sensor" instead of a MAP sensor ???

Bob

 

when i turn the key on the relay clicks immediately once and then clicks again after a second or two and then immediately after it clicks the second time there is another click that sounds like it is coming from the high pressure fuel pump, but i don't think the high pressure pump is actually kicking on ... no buzzing sound or vibration, just the click ... the in-tank or low pressure pump is actually on a toggle switch under the dash ... not sure why, it was like that when i bought the truck but the in-tank pump kicks on with the toggle switch and seems to run fine ... i checked the fuse and it is fine

 

oh, and yes it is a MAP sensor ... sorry