I have a 2003 ford ranger xlt with a 4.0L v6 engine. It is my first car and dont expect things to run perfectly. It has 147,400 miles. Since we bought it from a friend, it has had a rough idle and trouble going uphill. It also has trouble going between 40-50 mph steadily. It had a misfire in cylinder 1 with the error P0301 and the check engine would flash. We disconnected the battery and had it serviced so the light isnt on.

With the service we got a brand new air filter but the idle as well as bogging still occurs. I would like to know what could cause this (most likely cause)

 

With the misfire only being on the number one plug, first you should pull the #1 plug and inspect it. A new set of wires wouldn't hurt. If that doesn't help then let us know.

 

Welcome to FTE.

Post All trouble code Numbers, as they can offer up good trouble shooting clues. Disconnecting the battery B- cable to wipe the trouble codes & turn the CEL off, doesn't fix a problem, but could actually cause driveability problems for a day or so, (if you didn't go through the cold & warm idle relearn proceedure afterward) as it'll wipe the KAM, in which the base idle strategy is stored & take a few drive cycles for the computer to relearn its idle strategy.

The flashing CEL indicates a cyl misfire & the P0301 code says the computer is unhappy with cyl-1, so for now focus on the cyl-1 misfire.
A number of things can cause this, from a bad plug or plug wire as has been suggested, to a dirty, faulty fuel injector, sticking or burned valve, internal coilpack problem, to, well you get the idea, you need to do some diagnostics on cyl-1 to see what gives with it. Like a plug inspection & deposit read, as has been suggested, to maybe a vacuum gauge & maybe a compression test.

Any idea how long its been driven with this problem???? Driving it with the misfire means the cat converter has to process the unburned fuel, so that can cause it to over heat & damage/melt its internal ceramic matrix & that can cause excessive backpressure, that'll cause the engine to bog & or to run hot, all a vicious circle!!!!

Any idea where the vehicle is on all past & present due scheduled replacement maintenance items, like plugs, wires, filters, PCV valve, fluids, ect & has the scheduled maintenance been kept up on time, over the years???

 

i checked the fuel injectors and it seems like the one for cylinder 1 is bent at a different angle. i looked at the other ones and they are all straight up and down except for that one, i just dont know what could cause just that one to bend.

 

Sounds like you have a good suspect for your list. Does it appear to be the same brand/make & squirt rating as the others??? Maybe someone has had this puppy out & didn't get its "O" ring properly seated.