2004 Expedition 5.4 has hesitation at idle after plug change

[jruppert]

Well I did a plug change today. It really wasnt that bad. I let the air pressure out of front tires and it lowered probably 7 inches or so. Furthest plug in back on passenger side was the hardest to get to but wasnt impossible. Anyway, truck has 226k on it and as far as driveability it ran pretty good but felt sluggish. Gas mileage was around 12 on highway. I replaced the plugs with the OEM Motorcraft. I did not replace the coils. I gapped plugs at .053. Original plugs looked pretty worn out but were gapped around .045. I thought that was rather odd. BTW, ive owned this Expedition for only a couple months. So I replace the plugs and noticed right away that it has a bad miss or hesitation at idle. First start and the engine was shaking quite a bit. I knew there was an issue at that point. I checked for vacuum lines and made sure all harnesses were plugged in. I couldnt find anything. I needed gas so I filled tires up and drove it to the gas station. It had a horrible hesitation at idle to approx 2000 rpm. After that it went completely away. I put gas in it and drove it around. I put around 10 miles on it and never saw a CEL come on. It does appear that the hesitation is improving. Overall rpm band is actually pretty good. It has a lot more pull when kicking it down into lower gear. Pulls a lot better at 55 as well. So what gives? Anyone have any thoughts? My theory is that when I had the fuel rails off maybe some dirt or something dropped into the intake and injector is being funny. Like I said, the hesitation is improving but I can still feel it. When sitting at idle you cant even feel it. Its only when you hit the throttle to take off. Any thoughts? Also, I found this line connected to my brake lines today while working on it. It has no end to it, as if its broken. Anyone know where this may go or suppose to go. Thanks

 

[Reconracer]

Well I did a plug change today. It really wasnt that bad. I let the air pressure out of front tires and it lowered probably 7 inches or so. Furthest plug in back on passenger side was the hardest to get to but wasnt impossible. Anyway, truck has 226k on it and as far as driveability it ran pretty good but felt sluggish. Gas mileage was around 12 on highway. I replaced the plugs with the OEM Motorcraft. I did not replace the coils. I gapped plugs at .053. Original plugs looked pretty worn out but were gapped around .045. I thought that was rather odd. BTW, ive owned this Expedition for only a couple months. So I replace the plugs and noticed right away that it has a bad miss or hesitation at idle. First start and the engine was shaking quite a bit. I knew there was an issue at that point. I checked for vacuum lines and made sure all harnesses were plugged in. I couldnt find anything. I needed gas so I filled tires up and drove it to the gas station. It had a horrible hesitation at idle to approx 2000 rpm. After that it went completely away. I put gas in it and drove it around. I put around 10 miles on it and never saw a CEL come on. It does appear that the hesitation is improving. Overall rpm band is actually pretty good. It has a lot more pull when kicking it down into lower gear. Pulls a lot better at 55 as well. So what gives? Anyone have any thoughts? My theory is that when I had the fuel rails off maybe some dirt or something dropped into the intake and injector is being funny. Like I said, the hesitation is improving but I can still feel it. When sitting at idle you cant even feel it. Its only when you hit the throttle to take off. Any thoughts? Also, I found this line connected to my brake lines today while working on it. It has no end to it, as if its broken. Anyone know where this may go or suppose to go. Thanks

Post a pic of the line; COP would be the next item to check.

 

[jruppert]

Sorry, dont mean to sound 'dumb' but what line are you referring to?

 

[rburch]

As far as the rough idle and hesitation i would start by disconnecting the neg battery terminal to reset the comp and run it through the drive cycle and see if that helps. If that does not help the next thing i would tackle is the COP. I would have done them with the plugs but to each his own.

The pic you posted is the cruise control disconnect switch. Not sure where it goes?

 

[jruppert]

I would have replaced the COPS but I didnt have enough money. On the drivers side, I remember getting a little bit more anti seize on a plug. I wonder if some of it got close enough to the electrode. I have been dwelling on this possibility. My wife drives it to work every day and so I took it for a run tonight. The hesitation is pretty minimal but you can still feel it a little. It is a huge improvement over what was.

I told my wife to take it to Autozone the other day and have them check to see if codes were present. I never saw a CEL come on but I figured what the heck. So she went there and they asked if the light was presently on. She said no. They refused to hook it up. They told her that it needs to be on for them to get a code. It irritated me just a little. All that light has to do is come on and go off and there is a code present. I am thinking I may just avoid them from now on.

 

[rburch]

If you disconnect the neg battery cable it will erase any stored codes and reset the comp causing it to have to relearn air fuel, idle speed, etc... could get rid of the slight hesitation! Could also try cleaning the throttle body and look for possible vacuum leaks.

 

[Reconracer]

Sorry, dont mean to sound 'dumb' but what line are you referring to?

My mistake, you posted the picture...sorry bout that

 

[Reconracer]

I would have replaced the COPS but I didnt have enough money. On the drivers side, I remember getting a little bit more anti seize on a plug. I wonder if some of it got close enough to the electrode. I have been dwelling on this possibility. My wife drives it to work every day and so I took it for a run tonight. The hesitation is pretty minimal but you can still feel it a little. It is a huge improvement over what was.

I told my wife to take it to Autozone the other day and have them check to see if codes were present. I never saw a CEL come on but I figured what the heck. So she went there and they asked if the light was presently on. She said no. They refused to hook it up. They told her that it needs to be on for them to get a code. It irritated me just a little. All that light has to do is come on and go off and there is a code present. I am thinking I may just avoid them from now on.

I actually have my original COP's. My issue was plugs but I changed my COP's first (EBAY $110 shipped if I remember correctly). I'll see if I can scrounge them up for you...

 

[ELVATO]

If you disconnect the neg battery cable it will erase any stored codes and reset the comp causing it to have to relearn air fuel, idle speed, etc... could get rid of the slight hesitation! Could also try cleaning the throttle body and look for possible vacuum leaks.

This is what I was thinking, too. Maybe you should have disconnected the battery so the engine could "learn" the new plugs? Could explain why the hesitation has been going away as the engine may be in the process of doing so?

 

[mindgame]

Also, I found this line connected to my brake lines today while working on it. It has no end to it, as if its broken. Anyone know where this may go or suppose to go. Thanks

I came across it also.. Never fullly tired to locate where the other end goes, but I assumed that it just maybe a vent line for the IWE line.. dunno..

 

[jruppert]

Thanks for your suggestions. I really didnt think about disconnecting the battery. I will try it this weekend. I thought about purchasing some seafoam and seeing if that helps any too.