I have a 99 4.6 Expedition with 87000 + Miles. Eng stumbles at about 35MHP and 60MHP if I let off the gas then press it again it goes away untill I reach that speed again. I just put in new pulgs and wire about a month ago. Also I had it checked and there are no code or check Eng light on please give me a clue...

 

I had the same problem with my 2000 5.4L, it was a coil on the back plug (passenger side back plug). I was told this is common that the heater hose leakes on it and it shorts out. It solved my problem.
Tony
tonyk96(No Email Addresses In Posts!)

 

Thanks tonyk. I just took it out for a drive and noticed its not so much the speed but the RPM's it happens at about 1300-1500 was this about the same for you?

 

Thanks tonyk. I just took it out for a drive and noticed its not so much the speed but the RPM's it happens at about 1300-1500 was this about the same for you?


Yes, It seemed the harded I pressed on the gas the more stumble I received during that RPM.

Tony

 

Thanks but I dont have COP on my 4.6

 

Fulton,

It is time to change you spark plugs and wires if you haven't already done so. Make sure to use good quality double platnium plugs, aftermarket is just as expensive as ford, so i'd recommend using motorcraft plugs. Again they MUST be double platnium. If you're paying 1-2bucks a plug they aren't the right ones. And get a good quality set of plug wires (not cheap but worth it). This should take care of your problem. I don't know how mechanically inclined you are, but if you choose to change them yourself, i'd recommend changing one plug wire and plug at a time. Once you remove the boot, blow some compressed air into the plug cavity before you remove the plug. Water, dirt, and other stuff builds up in the cavity, and you don't want that in your engine. Take your time, and I'm almost positive it will take care of your problem. I hope this helps.

Dube

 

Thanks Dube that is just what I had planed for this weekend.

Fulton

 

Fulton,

While replacing your spark plugs won't hurt I don't think this will remedy your issue. The first thing I would do is change the fuel filter. This is easy if you know how to do. Write me back if you don't know how. If I don't check this forum soon write me at trowe76@sbcglobal.net

 

Well I havent done that yet and it does seem easy I'll try it.

Fulton.

 

It is very easy if you know how to do it. You will need a fuel line disconnect tool and your new filter. You will need rags to catch the gas spilage - it's minimal - and you will need goggles to protect your eyes. There is a fuse in your power distribution box (the one under the hood - driver side) for the fuel pump.. Take this out and try to start your car a few times. If it doesn't start then you are ready to go.. if it does start let it run until it dies. Oh and last but definately not least.. NO SMOKING! Have fun. I had a problem like yours and I switched out PCV valves anc cleaned sensors and throttle body and blah blah blah.. come to find out the fuel filter needed replacing.

 

Well I changed my fuel filter and it didnt help. Now for the first time I had a very time getting my Expy to start it had Batt power but seems not to fire after about 2-3 trys it fire and idles fine but the stumble is still there at abot 1500 rpm's. Let me add this it was colder this morning then normal but it fired up just fine firts thing it only gave me problems after I stopped and tryed about an hour later.

 

Plugs and wires brother. I do dozens of them a year with the same problem you are having. Fixes it every time. If it doesn't fix your problem, i'll buy you a coke.


Dube.