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david, Auto Service Technician
Category: Ford
Satisfied Customers: 1499
Experience:  Certified Master Technician,Certified in diesel & gasoline engines
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2002 Ford Explorer Sport Trac. 175k miles. Check Engine light on.

Resolved Question:

2002 Ford Explorer Sport Trac. 175k miles. Check Engine light on. Rough Idle. Random misfires at lmost any RPM or speed. Have replaced: Fuel Filter. EGR Valve and EGR Valve controler - Coil Pack - Plugs and wires. No visible or audible vacuum leaks. Interesting to not that I just started towing a trailer (4k of weight) and problem occured about 2 weeks after start of pulling the trailer. I am driving with OD turned off. Problem not as noticable when not towing the trailer so it leads me to believe that this problem has been going on for possibly longer than I think it has. Any ideas?
Submitted: 4 years ago.
Category: Ford
Expert:  david replied 4 years ago.
Hi thank you for your question I can hep.

Can you get me the code stored in the ECU? This will help pinpoint the problem.

Also did you replace these parts to fix the problem? Have you noticed and smoke from the exhaust?
Customer: replied 4 years ago.
I cleared the codes but I think they were 0301 0302. I do remember it said engine misfire bank 1 then engine misfire bank 2. Yes the parts I replaced were in an attempt to fix the problem. I felt thst misfire could mean bad plugs or wires. When that didnt work Auto Zone said to look for vacuum leak. Couldnt find one but I figured with as many miles as the truck has it wouldnt hurt to replace the EGR valve and controller. BTW when I disconnect the vacuum hoses from the control the engine idles alittle better.
Expert:  david replied 4 years ago.
P0301 = Cylinder #1 Misfire Detected
P0302 = Cylinder #2 Misfire Detected

These codes are saying the problem are related to #1 and #2 cylinder's. This could be related to the coil pack but it would be more then just 1 and 2.

From the info you gave about disconnecting the vacuum hoses.
This sounds like the Mass Airflow (MAF) sensors is either bad or dirty.


Airflow Meter/Sensor

Mass Airflow (MAF) sensors measure the weight and rate of air moving through a passage of a known volume or size. Typically, MAF sensors utilize hot wire or thick film technology. Signals generated may be analog or digital depending on manufacturer. As more air passes through the MAF sensor, the voltage or frequency increases proportionally. The EMS uses this information to calculate injector pulse-width and spark advance. Performance issues from MAF sensor failures range from no-start conditions to stalling, hesitation, stumble and improper air/fuel mixtures.

A faulty MAF sensor due to loose connections, bad grounds, high resistance in the circuit, or opens in the circuit can cause the following symptoms.

Related Symptoms
  • A no start condition
  • Stalls at idle
  • Surging of idle
  • Extended crank time when engine is cold
  • Hesitation
  • Stumble
  • Chuggle
  • Poor fuel economy

graphic
The location of the Mass Air Flow (MAF) sensor (3), the electrical connector (1) and the retaining bolt (2)


It is not recommended to try to clean the sensor but remove it from the air duck and see what it looks like. You can try vary carefully using brace cleaner or alcohol to clean it.


Hope this helps
david, Auto Service Technician
Category: Ford
Satisfied Customers: 1499
Experience: Certified Master Technician,Certified in diesel & gasoline engines
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