Hi I am new at this but I hope someone has had this trouble before and can help me I ve got an 03 ranger 3.0 flex fuel. when I bought the truck it had been ran hot but came with two new heads so I bought the gasket set water pump, thermostat, plugs and wires. put it all together started it fill with antifreeze let it run for about two hours ran perfect turn it off the next day I recheck the water and oil all looked good went for a ride now the problem after it runs at 2000 rpms for 1 min it starts misfiring you can let it idle for a min or so and it smooths out. would this be the cam sensor? Thanks for any help

 

Now hit ebay for $23.oo coil pack. Disconnect positive battery cable and jumper it to the negative for an hour to force reset the Brain. 2 plugs fire from each double ended coil with 40 KV used up to fire each plug and the engine block making up the ONLY other electrical path. Electricity is lazy and will take the path of least resistance. When a spark plug fouls the 40 KV spark does not happen. What does happen is that 40KV is added to the other 40KV for 80KV. That 80KV will find some place to go. The shorted plug now makes the engine block ground to the 80KV. The carbon ignition wire insulation fails, pin holes and arks. So does insulation in the coil pack. You get a P0305 - OBD-II Trouble Code. "misfire" refers to an incomplete combustion process inside the cylinder. Variation over 2 percent will illuminate the Check Engine. Mechanical problems do not fix themselves. Electrical responds to a lot of parameters, Think, but keep it simple. Double check all if your wiring connectors wiggle the wires did anything happen while you were replacing the heads.

 

thanks for the reply. Nothing happen on the head swap it went smooth I have double checked all wire connectors and they seem fine I will hook code reader to it later today and check for the po 305 code and ill disconnect battery and jump to reset. Ill let you know what I find thanks again

 

Disconnecting battery needs to be done when working on any vehicle, but it won't reset the computer, it did on the older EEC-IV(OBD1, 1994 and older) but not on the newer EEC-V computer(OBD2, 1995 and up)

Yes, Ford Ranger 3.0l did have some bad coil packs on the early 2000's, so not a bad change.

High idle at start up is normal, Choke Mode, idle RPMs are based on outside temp at time of starting(coolant temp in engine really), at 50degF 1,200 rpms, 32degF above 1,500
Automatics idle higher than manual trans vehicles

2,000 seems high but never owned a 3.0l, it is a high RPM engine, best torque at 3,500, my 4.0l is 2,500rpm.
So 3.0l simply needs to be run at higher RPM in general use.

Were the new heads "new"?
The ranger 3.0l 2004-2006 heads had bad valve seats causing misfires but usually only after many miles of use.

My 4.0l only likes Motorcraft or Autolite spark plugs, other brands work but I do get misfires cold and they wear out sooner.

3.0l does use the Ford Waste Spark system, so yes 2 spark plugs fire each time, so 1 spark is "wasted".
This means you should use regular copper plugs or Double Platinum, don't use single platinum, it would be a waste of money.

Crank position(CKP) sensor sets base timing of the spark and fuel injectors, if it doesn't work then engine doesn't start.
Cam Position Sensor(CPS) fine tunes fuel injection and aids in spark advance and retard.
If CKP and CPS were "out of time" you would get a CEL(check engine light) fairly quickly.
CKP sensor is dominant, so computer would ignore CPS and turn on CEL if there was a problem.
Engines ran fine for many years without CPS, these were added for better MPG and emissions.

So no, probably not CPS issue, but on the 3.0l the Cam Synchro housing(what CPS sits on) does wear out, and needs to be changed every 80k-100k miles.
This also runs the oil pump, so very bad news if it fails while driving, it will usually start making a squealing noise when bushings inside start to wear out, "usually" being the key word in that statement, lol

 

Thanks for all the advice guys it was the coilpack replaced it today drove it 15 miles and it ran great. It was just odd that it misfired justbetween 2000 and 2500. But thanks again for your help.

 

Thanks for the update and the fix, it will help others