I have no idea if this is the right place for what Im about to ask, if it isn't I do apologize. I am a new member here so first I would like to say hello and it is a pleasure to meet y'all :). Ok, now with the question. I own a 2002 Ford Ranger Edge 3.0l v6 RWD and am having some weird misfire issue. It seems to be an inconsistent problem because it changes its characteristics at times. When cold, it runs like crap. Vibration when idling, hesitating and bogging when accelerating/driving, etc. When its warm it is a little better, still hesitates but not as much. When driving, smooth sometimes then rough at others, and that's with cruise control on, holding the same speed, so Im pretty sure its not just me messing with the engine. The check engine light goes back and forth between staying solid and then blinking. Also, when the problem first occurred, it wouldn't go past 2500 RPM. Now it wont go past 3,000 RPM. Its like it has a 2 step. I dont get it, I have replaced spark plugs and both upstream o2 sensors. The downstream one is kinda stuck in there tho so I couldn't replace that one. At one point, I had the number 2nd spark plug wire on the driver side disconnected and the engine almost ran smoother. I think I am only on 5 cylinders. What do I do? Has anyone else had this problem? If so, what is the solution? Thank you in advance :)

 

Check engine light?? do you have a code reader thats where to start.......... plus miles on your engine.......

 

+1 ^^^, see if there are any Codes, auto parts store will read them for free, WRITE THEM DOWN!!!!!

CEL(check engine light) doesn't need to be on for there to be codes in memory

Make sure you have correct firing order
On the coil pack one side will be 1-2-3
The other side is NOT 4-5-6
It is 5-6-4

1-2-3
5-6-4

Or

3-2-1
4-6-5

1 and 5 must be together, as must 2 and 6, and 3 and 4
Its the way the engine is balanced

Cylinder numbering is
3 6
2 5
1 4
front

Make sure wires are also correct



Vacuum leaks
Easy test for vacuum leak, warm up the engine, 10 min drive
Let it idle and open the hood
Unplug IAC Valve's 2 wire connector, it will close
Idle should drop down to 500 or engine may even stall, either is GOOD, no air leaks
If RPMs do not drop then you have a leak

IAC(idle air control) Valve is located on upper intake near throttle plate, it is used by the computer to set idle RPMs
Cold idle should be 1,100 or so, the colder it is the higher the idle is set
As engine warms up idle will go down, with warm engine 700rpm, if automatic trans then 800rpms



ECT(engine coolant temp) sensor
Computer uses this to set the high idle when engine is cold, it is also used for CHOKE Mode
Cold engine still need to be Choked even when fuel injected, which means run Rich with high idle
If computer "thinks" engine is warm because of a problem with ECT sensor, then engine will not have a high idle and will struggle to run until it does warm up

ECT sender, this is used for the dash board temp gauge, not to be confused with ECT sensor, they look similar but are NOT the same, sender uses 12volts, sensor uses 5volts


Restricted RPMs can be 2 things
Limited fuel flow, dirty fuel filter, engine can't get enough fuel

Partially clogged exhaust pipe, if exhaust can't get out then new fuel can't come in so you lose power.

3rd thing is rare but possible, neutral switch, if computer "thinks" transmission is in Neutral, then it won't allow RPMS to go above 3,000, called an RPM Limiter
This switch is different for manual or automatic trans, so need to know what you have