1992 f150 4x4 5.8 efi 5.8 e40d transmission
can someone please tell me how to tell if the map sensor is bad?
my truck would not idle, i changed the tps,ect, iac. I have checked for vacuum leaks and put in new sparkplugs and wires. if i pull the vacuum line off the map sensor, the engine smooths out and idles fine, but shifts a little rough
If you do not have or cannot afford to buy a hand vacuum pump or tachometer, you may be able to rent one in a major auto parts or equipment rental store.
1. Set the tachometer to the four-cylinder scale
(regardless of how many cylinders the engine has).
2. Connect one tachometer lead to the middle terminal
on the MAP sensor and the other tachometer test
lead to ground.
3. Connect the two jumper cables the same as before,
attaching each end terminal on the sensor to its
respective wire in the wiring connector.
4. If you want to measure engine vacuum so you can
correlate it to a specific frequency reading, connect
a vacuum gauge to a source of manifold vacuum
on the engine, or tee the gauge into the MAP
5. Turn the ignition ON and note the initial reading.
The reading on the tachometer should be about
454 to 464 at sea level, which corresponds to a
frequency output of 152 to 155 Hz.
6. Start the engine and check the reading again.
If the MAP sensor is functioning properly, the
reading should drop to about 290 to 330 on the
tachometer, which corresponds to a frequency
output of about 93 to 98 Hz. No change would
indicate a defective sensor or leaky or plugged
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