1999 Ford Expedition misfire

Tiny
RICHARDWARD
  • MEMBER
  • 1999 FORD EXPEDITION
Engine Performance problem
1999 Ford Expedition V8 Four Wheel Drive Automatic

the car has had it's plugs and wires changed but car is still misfiring firing order is correct and coils are still good what do I try
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Friday, December 5th, 2008 AT 6:11 PM

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Tiny
DAVE H
  • EXPERT
Check and clean or replace CKP

Crankshaft Position (CKP) Sensor (4.6L)On lower front of engine. .
Crankshaft Position (CKP) Sensor (5.4L)On lower front of engine.
Models Equipped With Coil Pack(s)
The EI system consists of a Crankshaft Position (CKP) sensor, coil pack(s), related wiring and PCM. The CKP sensor is used by the PCM to indicate crankshaft position and speed by sensing a missing tooth on a pulse wheel mounted on front of crankshaft. The coil pack(s) receives its signal from the PCM to fire at a calculated spark target. Each coil within the pack fires 2 spark plugs at the same time. The plugs are paired so one plug is fired on the compression stroke, and the other plug fires the mating cylinder, which is on the exhaust stroke. On the next cycle, firing strategy is reversed.
The PCM acts as an electronic switch to ground in the coil primary circuit. When the switch is closed, positive battery voltage applied to the coil primary circuit builds a magnetic field around the primary coil. When the switch opens, power is interrupted and the primary field collapses inducing high voltage in the secondary coil winding and the spark plug is fired.


http://www.2carpros.com/forum/automotive_pictures/266999_crank_2.jpg

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Friday, December 5th, 2008 AT 6:34 PM

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