Tuneup or Transmission or ?

[Solid_Hit]

2003, V8 5.4, 130,000, Eddie Bauer.

At 40mph (a little less or a little more), if I am coasting and give her some gas, I get a lot of hesitation and a kind of stumbling. It doesn't happen at any other speed or if I am accelerating from a lower speed, only if I am holding that speed and ask for more.

I don't get any hesitation when I'm pulling my horse trailer.

Tuneup or transmission or ?

 

[Thermo]

Solid, sounding like a COP to me. Granted, if you have over 60K miles on the plugs, then it may not be a bad idea to do a tune up and check the COPs as you are doing the plugs. If you can make the truck stumble, keep your foot into it to force the CEL to come on. This will help you narrow down the cylinder in question if it is an engine issue.

On a side note, since it is only happening around 40 mph, try turning off the overdrive and then seeing if things act differently. I only mention this because it is a known fact that the 1st gen trucks could have issues at 40-45 mph when you gave the truck a little bit of gas because there was a programming concern with the tranny and it would cause the truck to hunt for the correct gear, resulting in it flashing the overdrive light at you. Ford fixed the issue in the later trucks, but this is sounding like something related to that in the fact that Ford fixed the programming by forcing the truck to stay in a gear and this is what you are seeing now.

 

[Solid_Hit]

Thanks for the reply. I've already had the problem with the overdrive light and had it fixed. This occurred after the fix.

What is a COP and CEL?

 

[toms89]

Thanks for the reply. I've already had the problem with the overdrive light and had it fixed. This occurred after the fix.

What is a COP and CEL?

Coil On/Over Plug

Check Engine Light

 

[toms89]

It sounds as if maybe you are in overdrive and not giving it enough gas to downshift?! If this is the case the low rpm and tall gearing puts a heavy load on the motor and if you feel a stumble it could very well be an ignition miss. I would change plugs and fuel filter if you have not for some time then go from there. Check the cops while you have them off for signs of corrosion on the spring inside the boot or any cracks on the housing.

 

[Solid_Hit]

I forced the problem yesterday and if I take off overdrive while having the problem the rpm (of course) went up but the problem went away.

I've also noticed that it has begun to idle a little off while at a light. I bought the truck with 106,000 from Car Max and I have no idea if there was a tuneup done. I pull a horse trailer at least once per week but otherwise just drive to work or the stores. (Took one trip to NYC last year to visit family - ~1,800 miles round trip). Truck uses some oil too - a quart every 800 miles or so.

 

[toms89]

I forced the problem yesterday and if I take off overdrive while having the problem the rpm (of course) went up but the problem went away.

I've also noticed that it has begun to idle a little off while at a light. I bought the truck with 106,000 from Car Max and I have no idea if there was a tuneup done. I pull a horse trailer at least once per week but otherwise just drive to work or the stores. (Took one trip to NYC last year to visit family - ~1,800 miles round trip). Truck uses some oil too - a quart every 800 miles or so.

Turning overdrive off lowers the effective load so it is easier to fire. (Load equals resistance to fire for your spark plugs) Since it is unknown if the spark plugs were ever changed I would start there. The spark plug gap will open up with age also making it much more difficult to fire.

 

[Solid_Hit]

Thanks! Will give it a try this weekend.