This may be an age old problem but I'm in dire need of assistance:

1998 Expedition 4.6L with K & N FIPK and Flowmaster 50 series muffler.

My check engine light came on for the first time since I have had the truck. Went from flashing to solid and back to solid again.

Rough idle and hardly any power during higher speeds (45-60).

Reset the computer (unplugged the negative battery cable etc) The CEL is not on anymore, but I get rough accelration.

Also the rough idle only occurs in gear, not park or Nuetral

This all happened overnight, it ran smooth as a whistle yesterday. We had a heavy rain overnight as well.

Any suggetions?

 

Try a search on "rough idle" and you'll find lot's on good info. The most common culprit seems to be the Idle Air Controller (IAC). Replacing mine fixed my rough idle but I didn't have the loss of power that you describe.

chknbone

 

I dont think you can get it pulled now until it comes back on again, but you can get your code pulled for free at autozone.

Get the code from them, and come back here and search for the code.

 

Well this morning I cleaned the IAC. It was filthy, it idles better but when I give it gas when I am in gear it still "flutters."

I just had a tranny flush and an oil change and it was running fine after both (a week ago).

This just started overnight. I do remember buying 91 octane Chevron gasoline on Tuesday, but this problem did'nt occur until Saturday. It only has 62500 miles on it also.

 

Someone else may have a better idea, so for now all I can say is see if the CEL comes back and take your expy to autozone and ask them to pull the code for you.

Im not sure if the codes are stored even after you reset the computer or if it just gets the computer to stop displaying the CEL...but Im guessing the its the first.

Good luck.

 

You have a misfire on one or more of your cylinders. Probably due to the heavy rain. Remove your plug wires and blow down in the hole with an air compressor then put some plug boot grease on them and put them back on. I would check #4 first it is on the back passenger side. Good luck!

 

It turns out that it was plug number 4. I bite the bullet and bought a code reader. a 99$ investment that is well worth it. Now the hard part is getting to that plug. Any suggestions???

 

lots of extensions and swivels :\

The spark plugs are a real PITA to get to...even the fronts.

 

that's why Mr. 98 is going 2 get a full service tune and not worry about any of that. My knuckles are plenty bloody already.

 

Just this weekend, I was driving my newly-purchased high-mile F150 back from the seller, and I stopped for gas. Started it back up again, and it idled rough, like it was missing a couple cylinders, and would'nt get up to speed (I held it at 55, and it had no power there). The CE light flashed, then went steady, then flashed, etc.

I had about 250 miles to get home, so just kept driving it, and then about 100 mi later it started to run normal again.

The dealer where I picked it up said the PO just changed an O2 sensor, but that there were 2, one for left and right "bank", I think he said, so he said the other "bank" sensor might go out soon.

I'm going to take it to the dealer to have them check it out, but at least it's running smooth now.

 

After hours of brain twisting questions I decide 2 buy a INNOVA computer scanner which will read any and all codes give by the Exp's computer. The code read there is a misfire on plug #4.

So I decide 2 buy plugs. Knowone told me that plug 4 was aaaaaaaaaaaaaaal the way in the back (not 2 far from Egypt) I 86ed the plug idea and took it 2 the dealer. Good thing my baby works there and has a HUGE discount....

Turns out it was the Coil Pack which had gone bad. My plugs & wires were fine.... so $150 later.. I am back on the road.

Lesson here... always trust your woman and never trust yourself... lol...thanks guys 4 all your help!!

 

Thanks all for all the postings! I just had a problem yesterday while comming home. MY 5.4 99 F150 started to, what appeared to be a miss, or a shuter???? At an idel it sEEMED to be ok and only appeared under exceleration????? Engine service light came on. On the way to get the codes read, I tuned my AM radio to a frequency that was not being used and only heard "hash". I could hear the tit, tit, sound of the miss fireing every so often. It was hardley audiable at an idle( engine seemed to idle ok). It turned out to be an intermient #4 coil pack (NAPA $40). Here is the ratchet set up I used to change the plug while I was there. Spark plug deep well,3'entension, universal, 12" extension. all taped together. To start the new plug, I used the deep well with the 3' extension than the universal, however I taped the universal so it would not swivel(like a one inch extension). Than I was able to hand thread the plug using the taped end. It worked well for me and may for you. Listening to the radio may give you a clue if it is electrical.... Hope this helps!

 

i changed all plugs on my 98 4.6L, there not that bad when you set your mind to it. don't sike yourself out. used a standard plug socket, 3" ext, 12" ext, a universal, and a 12" ratchet with a universal handle, and a piece of vacuum hose for inserting plugs(it's cheap bendable and you can't cross thread) and believe it or not plugs 1- 4 are the easiest. you dont have to remove anything.plugs 5- 8 you have to remove the power steering resivor brackets and the brake booster vacuum lines are in the way.

how much did the innova cost you.

 

Research further!!! The #4 coil goes out more than any other due to a leak from the heater hose mounted directly above it. Be sure to check the fitting and put a new clamp on if necessary. It will save you a lot of aggravation replacing it again.