2003 4x4 4.0 liter with 90,000 miles misfires when it is cold and damp outside. My truck has been doing this intermittently but it's getting worse. Whenever the temperature is right around freezing and it's raining or snowing the engine will misfire. It happens above 40 mph, never when driving slow, never when it's below 20 degrees, and never when it's above 40 degrees. There are no codes being thrown and the check engine light does not ever come on. Hooked up the computer with a Ford mechanic and it's happening on all cylinders. Replaced the ignition coil and plug wires with motorcraft parts and the truck is still misfiring. Any ideas?
may not be getting enough gas. try changing your fuel filter. it could be clogged. my truck used to have a rough idle and it would run the same way at around 45mph or when its cold outside. i changed the fuel pump and filter and the problem is gone.
is it hard to start sometimes?? like motor turns over but takes a bit to fire..... if so its a common problem on a 01 to 03 4.0. the fuel pump gets week and also the fuel rail sometimes has to be changed. that could have something to do with your problem
maybe a fuel problem like to much water in fuel id try going to a different gas station and getting some fuel line antifreeze
Never tell people how to do things. Tell them what to do and they will surprise you with their ingenuity."
General Geroge S Patton
automatic trans, 4.10s with L/S
ported and polished TB
4brand new speakers with inslation in doors
smoked tail lights
20%tint on driver and passenger windows
5% tint on back window
Thanks for all the suggestions... I brought the truck to Ford and they found oil on the mass air flow sensor from my K&N filter. The mechanic cleaned the sensor and replaced my air filter with a stock one. He suggested not using a K&N because of the oil issues. Not sure if it's because of the location of the maf sensor or what... but I've used K&N filters on my vehicles for the last 10 years and I've never had an oil problem before. I'll update the post with the results.