rough idle 4.6

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May 15, 2013 | 07:40 PM

flamingx

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rough idle 4.6

I have an '03 Explorer with the 4.6 2V I have only owned for a month. Shortly after I bought it I found it doesn't like to idle for more than a few minutes and would throw "system too lean" (both bank 1&2) codes.

At first when it started it would get really bad ignition knock so I cleaned the MAF and it ran fine for couple weeks. Then a couple weeks ago while sitting in a drive thru the idle slowed right down and stalled, so I restarted it and it would not stay running unless I revved it up, still throwing the same codes. I replaced the fuel filter (couldn't even blow through it)

It has run really well uptil this afternoon, sitting at a red light it started to lop (it sounded like it had a real lumpy cam), so far no engine light.

Anybody have any ideas before I spend a ton of time and money replacing all the sensors, gaskets and complete fuel & ignition systems.

May 20, 2013 | 03:13 PM

F250CCowner

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Bad COP or a vacuum leak somewhere. Was the engine steam cleaned before you purchased it? Meaning now it is spotless for a 10 year old vehicle. If so they probably shorted out a COP. Either that or you have a vacuum leak from one of the rubber hoses rotting away. They do break down over time and around the ten year mark is when it happens.

May 20, 2013 | 08:51 PM

flamingx

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I did a few visual checks for vacuum leaks, around the intake atleast, due to the 'System too Lean' codes it kept throwing and couldn't find any.
It's not throwing any 'Miss fire' codes (yet). I will hopefully finding the time to put some new Motorcraft spark plugs into it in the next few days and will be check resistance on the coils at that time. Thank you for the suggestions

May 21, 2013 | 11:13 AM

F250CCowner

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A bad coil pack won't always throw a code. Especially if the engine was power washed and water got down into the plug well. Also replace all the plug boots while you are swapping plugs. They are cheap and easy to swap out at that time. They tend to crack over time because of the heat in there.

May 25, 2013 | 10:55 AM

flamingx

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Update; finally got time to change the plugs. The old ones look fairly new but were NGK (I don't about NGKs but I have found these newer Ford OHC engine only seem to like Motorcraft) the gaps were anywhere from .050-.060 (.052-.056 is recommended) boots where newer as well. The Throttle Body was in the way so I removed and cleaned that while I was in there.
Not to mention, I had to unplug and plug back in quite a few vacuum lines to do all this as well.

It runs 10x better now with smooth idle and no hesitation. So I'm not sure if it was a vacuum leak, the dirty TB, a problem with the plugs or the couple plug boots that weren't on right. So until another gremlin rears it's ugly head, it seems to be problem solved.

Jul 15, 2013 | 08:23 PM

bigbuilder

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I had the same problem and it was the plug boots

Jul 23, 2013 | 03:30 PM

deltasoft2009

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I had rough iddle and grabbed some intake cleaner and cleaned the intake the most i could....improved by 100%!! paid 300 buckz as was afraid to do plug swap on my truck--too small of spark plugs--and lot of miles.