sputtering and misfiring
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Senior User
Joined: Aug 2010
Posts: 189
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From: Port Washington, Wi
sputtering and misfiring
ok so ive got this 90 f 150 4.9 5 speed, just bought it anfter it had sat for half a year. I put in a new clutch and start it up and it runs and drives but the engine kind of pops at idle and sputters under load while trying to drive it. pulled the codes and it comes up with map sensor out of range. anyway i unplugged the map sensor and it runs great other than a high idle and no low end. i tried 3 other map sensors with the same result, the wires going to it look perfect and im stumped. Please help!!!
Fleet Owner
Joined: Oct 2005
Posts: 20,785
Likes: 1,751
From: Kentucky
Have you tried pulling the codes from the PCM to see what it THINKS is wrong? Have you verified vacuum is getting to the MAP sensor? Have you verified the wires running from the MAP sensor to the PCM are good?
Thread Starter
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Senior User
Joined: Aug 2010
Posts: 189
Likes: 1
From: Port Washington, Wi
ok yes i have pulled the codes. it came up with number 22, map sensor out of range. im not sure what the voltage should be at the wires with the sensor unplugged but with the key on engine off i was getting 4.97 volts from 2 of the 3, not the ground. and yes there is vacuum getting to the sensor
Fleet Owner
Joined: Oct 2005
Posts: 20,785
Likes: 1,751
From: Kentucky
The output of the MAP sensor is a frequency not a DC voltage level. The 4.97 VDC you measured is most likely the Voltage Reference (VREF) signal.
Ryan has some great info here: Ford Fuel Injection Manifold Absolute Pressure Sensor (MAP)
Ryan has some great info here: Ford Fuel Injection Manifold Absolute Pressure Sensor (MAP)
Fleet Owner
Joined: Oct 2005
Posts: 20,785
Likes: 1,751
From: Kentucky
Looks like it's time to start tracing back wires to the PCM. This site has the pin-outs for several different years/models of Ford trucks: Ford Fuel Injection Truck Computer Pin outs
