1998 Ford Taurus Engne soon light

Tiny
SJOLY
  • MEMBER
  • 1998 FORD TAURUS
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 255,500 MILES
The light engine soon is on since few months. The code inside the PCM is RANDOM MISSFIRED. IT's not only 1 plug that is misfirrging.
I change the plugs and put a new set of wires ffrom ford on the car and still misfirred? WHY?
I would like to know where I could start to search to resolve the problem?
Thank you.
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Wednesday, February 4th, 2009 AT 11:51 AM

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Tiny
DAVE H
  • EXPERT
Hello. Thanks for the donation. Much appreciated

I would be checking the coils and the CKP sensor to start with !

ELECTRONIC IGNITION (EI) SYSTEM
NOTE:Ignition timing is controlled by the PCM and is not adjustable. DO NOT attempt to check base timing as false readings will result.

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.

Models Equipped With Coil On Plugs (COPs)
The EI system consists of a Crankshaft Position (CKP) sensor, Camshaft Position (CMP) sensor, individual COPs mounted directly on the spark plugs, 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 CMP sensor is used by the PCM to identify when piston No. 1 is at Top Dead Center (TDC) of compression stroke. This signal is used to synchronize firing of individual coils.
The coils receive their signal from the PCM to fire at a calculated spark target. Only one coil is fired at a time and only on the compression stroke. The PCM acts as an electronic switch to ground in the coil primary circuit. When the switch is closed, 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.
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Wednesday, February 4th, 2009 AT 8:08 PM

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