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Shawn, Auto Service Technician
Category: Ford
Satisfied Customers: 3756
Experience:  16 years experience Ford,Nissan and Honda dealership in all areas
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1999 F-150: triton..diagnostics..P303.Right valve cover..highway speed

Resolved Question:

I have a 1999 F-150 with a 4.6 L Triton engine which misses under highway load.
Dealer diagnostics prteseneted codes P301, P302, & P303.
Right valve cover reportedly leaked causing plug wires rto short.
All plugs and plug wires were replaced and tuneup performed.
Engine continues to miss under highway speed load.
It feels like a centrifugal advance failure of old.
Recommendations please!
Submitted: 7 years ago.
Category: Ford
Expert:  Shawn replied 7 years ago.






Thank you for asking your question on JustAnswer, my name is XXXXX XXXXX I will be assisting you today with your question. The most common cause of the problem you are having is a defective CMP (Camshaft Position Sensor), I am sending you instructions in pdf format, hope this helps you out.













DTCDescriptionPossible CausesDiagnostic Aides
P0300 - Random Misfire The random misfire DTC indicates multiple cylinders are misfiring or the PCM cannot identify which cylinder is misfiring.
  • Camshaft position sensor (CMP)
  • Low fuel: less than 1/8 tank
  • Stuck open EGR valve
P0301 through P0310 - Misfire Detection Monitor The misfire detection monitor is designed to monitor engine misfire and identify the specific cylinder in which the misfire has occurred. Misfire is defined as lack of combustion in a cylinder due to absence of spark, poor fuel metering, poor compression, or any other cause.
  • Ignition system
  • Fuel injectors
  • Running out of fuel
  • EVAP canister purge valve
  • Fuel pressure
  • Evaporative emission system
  • Base engine
The MIL will blink once per second when a misfire is detected severe enough to cause catalyst damage. If the MIL is on steady state, due to a misfire, this will indicate the threshold for emissions was exceeded and cause the vehicle to fail an inspection and maintenance tailpipe test.

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