2002 Ford Explorer Low RPM Bucking

2002 FORD EXPLORER
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NASMEYER
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I own a 2002 Ford Explorer 4WD with a 4.0 V6 and 80k miles. Recently I have noticed an intermittent problem when the engine is at a low RPM usually in OD between 40 and 55 MPH the engine will buck or mis fire a couple of times when driving a steady speed or accelerating slightly, it will become less noticable after I press the gas and drive the RPM's up as it downshifts and accelerates, this is not a constant bucking but will do it 1 to 5 times while in this RPM range. I have changed the air filter every 20k miles, just had the throttle body and injectors cleaned, I also cleaned the MAF sensor. I have not noticed any type of vacuum leak. No engine light has come on while I have had this problem. It has a very slight (barely noticable) but also intermittent mis during idle, but when I raise the RPM's at idle it runs smooth. At $100+ I am hesitant to replace the MAF sensor without being quite sure it is at fault.
Apr 6, 2007 at 3:33 PM
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JON BOY
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It sounds like the motor is missing when its loaded at low rpm's and not when your running it harder or taking off fast??

If that's what its doing, I would look at the ignition system. It sounds like its not getting a strong enough spark. If its missing enough, it should set a flag on the computer. Is the check engine light on?
Apr 9, 2007 at 6:09 AM
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NASMEYER
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[quote:69c27321d4="Jon Boy"]It sounds like the motor is missing when its loaded at low rpm's and not when your running it harder or taking off fast??

Is the check engine light on?[/quote:69c27321d4]

No light has come on at all while I have had this problem, if I accelerate real hard it will still have the miss at higher rpm's but is most noticable at low RPM's under heavy load.
Apr 9, 2007 at 7:37 AM
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PMYHAL
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I have same problem with Gand marquis did you fix it.
Apr 10, 2007 at 4:10 AM
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NASMEYER
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[quote:f11c7de835="pmyhal"]I have same problem with Gand marquis did you fix it.[/quote:f11c7de835]

Turned out to be plugs and plug wires, hope this helps with your marquis.
Apr 16, 2007 at 10:17 PM
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MERLIN2021
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The problem could be the EGR solinoid opening the egr at the wrong time. It's a small canister with 2 vacuum lines and 2 wires. Also if you can take the egr off and clean out the carbon in the passageway, use a coathanger and push it all the way to the throttle!
Apr 17, 2007 at 1:57 AM

Suggested Repair

The owner reported that replacing the spark plugs and plug wires fixed the intermittent bucking and misfire. If the miss returns, check the EGR solenoid for opening at the wrong time and clean carbon from the EGR passage.

Conversation Summary

A 2002 Ford Explorer 4.0 V6 bucked or misfired intermittently at low RPM under load, mainly in overdrive around 40-55 MPH, with a slight idle miss and no check-engine light. Maintenance already included the air filter, throttle body, injectors, and MAF. One reply suggested a weak ignition spark. The owner later reported that spark plugs and plug wires fixed it. An expert also suggested a mistimed EGR solenoid and cleaning the EGR passage.

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