Changed Plugs In my 05 explorer XLT 4.0L now it idles rough at low rpm idle. | Ford Explorer Forums - Serious Explorations

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Changed Plugs In my 05 explorer XLT 4.0L now it idles rough at low rpm idle.

Eric87

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City, State
sturgeon bay WI
Year, Model & Trim Level
05 ford explorer v6
So to start off Im new to working on Ford vehicles. Recently purchased this explorer, it ran well, but its got some miles on it so I decided to give it a once over and do some preventative maintenance. Air filter, oil change, the muffler had a hole in it so i put a new one on, and fixed the broken ground wire in the door and all went well. But after changing the plugs, which are motorcraft, I noticed it ran pretty rough at low idle rpm and would have a slight misfire, also felt like it had a slight power loss while driving but not as rough as when idling. Naturally I thought it was a issue with the plugs so I did some research on the forums read stuff about making sure to check the gap which I didnt at first so I pulled them out and gapped them to .052 (owners manual says gap spec is .051-.056). Still no change, I then thought maybe I had a bad plug wire so I replaced those and still no change. Then I thought maybe I had a faulty plug so I bought a new one and changed out the plug on the cylinder my code reader said had misfired and still no change. After that I though maybe I had a some weird fluke type of coil failure so I replaced the coil and again nothing changed. I feel Ive ruled out the ignition system, I quadruple checked my plug wire sequence. Now Im down to checking for a vacuum leak but Im not even sure where to start, all I can say is I need help. Im extremely frustrated because ive done this on other vehicles before with no issues, and in "fixing" something that wasnt necessarily broken I made it worse and Im having a hell of a time pinning down the issue here. At this point Im looking for any advice on what direction to proceed in before I swallow my pride and take it to a shop.
 



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I went through the same basic thing a few weeks ago, although I had a miss to begin with (due to some extremely worn out spark plugs). In my case it turned out I had 2 plug wires crossed at the coil. It took checking them 3 times to find the problem. If the wires are right it might be you cracked a plug insulator during installation.

Being new to working on a Ford had nothing to do with it. It's just one of those things you run into when changing spark plugs. I've been changing spark plugs and plug wires for over 5 decades and I still screw up once in a while.
 






Then I thought maybe I had a faulty plug so I bought a new one and changed out the plug on the cylinder my code reader said had misfired and still no change.

I feel I've ruled out the ignition system, I quadruple checked my plug wire sequence.
Agree with koda. 1-2-3-5-6-4 firing sequence on the coil pack is strange, and a very common mix up when the coil wires are removed all at once instead of one at a time..What p0300 series misfire code NUMBER(S) did your code reader find, and are the codes still present? Also, unless your 2005 is a Sport Trac, post in the 2002-05 Gen 3 sub forum. Very different vehicles.

OBD-II Diagnostic Trouble Codes (DTCs)
 






The code was p0301 and p0303 it definitely isn't the wires, as I said I checked them 4 times and even had a 2nd person check them for me as well. Also originally when I just changed the plugs only I did them one at a time to avoid mixing them up, I learned that lesson already. And I suspected a possible bad plug and went that route already with no change. Is advanced trac different than sport trac?
 






Just had same issue..... changed one at at time..... found 2 plug wires were not “ clicked” fully onto spark plug. I purchased new wires from rock auto, the old boots just didnt want to stretch over the plug. Hope this helps.
 






If we assume the wires are on where they belong, either you have 2 bad plug wires or 2 bad plugs (on cylinders 1 & 3). I'm a firm believer that the last thing touched is the last thing you f'd up. Changing plugs and wires can only effect plugs and wires. Something is wrong. The P0301/0303 codes indicate those two plugs aren't firing for some reason.

Did you use anti-seize on the plug threads? (you should w/alum heads). If so, were you careful not to get anti-seize on the electrodes? Getting anti-seize on the electrodes can short out the spark plug because it's a conductive substance.

Were you careful not to crack the ceramic part of the spark plugs when installing the plugs? It's easy to do if not using a spark plug socket or have the socket on crooked.

Did you put dielectric grease in the plug boots? Doing so allows the boots to go onto the spark plugs easier, seals out dust and water, plus it will help when removing plug wires in the future.

When the plug boots are installed correctly, you should feel a click as the metal part snaps onto the spark plug. If you don't feel the click, the wire isn't installed all the way.

Try switching the spark plugs and/or wires on cylinders 1 and 3 to cylinders 4 and 6 to see to the problem follows.
 






How about one of the NEW wires being faulty?
 






How about one of the NEW wires being faulty?

That's a possibility, but he's got 2 cylinders that aren't firing.
 






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