So I have spent about 3 grand on getting my sons Ranger to stop loosing power randomly. He would be driving and all of a sudden the truck would buck, chug and perhaps go into limp mode. Even flooring it in neutral would not go over 3000 RPMs. After 10-20 seconds it would come out of it. I have replaced everything.
MAF sensor
ERG
PCV
Plugs
Wires
IAC sensor
Fuel Pump
Fuel Filter
Intake Gaskets
Catalytic Convertors (front and mid, 4 total)
o2 sensors
exhaust pipe and muffler
I am sure I’m missing about 10 other things.

someone mentioned that the gas cap may be not venting correctly or something. So in a last ditch effort, I loosened the cap and now it drives like new. I can tell you the previous owner replaced the fuel filler hose and got rid of it shortly, like within a week later. I suspect that the truck was puking on him as well and dumped it.

it is a 2002, 4.0 SOHC, 4x4 auto super cab XLT.

I haven’t let him drive it for a month and today I said what the heck, I’ll try the gas cap trick and put 200 miles on it and it runs perfect.

any thoughts would be appreciated on how the cap is supposed to work with the EVAP system. Honestly I am to the point where I might just tell him not to click the cap when filling it up. I have 6500 total into his truck and probably is worth about 3 maybe.

thanks in advanced.

mike

 

How many miles on the truck\engine\tranny?
Considering you've now renewed so many parts & gotten very familiar with it
& that simular model\age used trucks are going for over $10k, think I'd keep it
& proceed to remedy the known quirks\weaknesses of the V6~4.0L~SOHC + 5r55e Tranny.
Might want to remove the bed & see exactly what the PO did with the FuelFill repair.

 

Thanks for the information, the truck odometer reads 216,000 miles. I don't know the history of the vehicle - meaning if the motor or tranny has every been replaced. The transmission shifts smooth and the color of the fluid is clear and does not smell burned. The oil has been changed every 3,000 miles and do have the information on that. It doesn't leak a drop or burn any oil/transmission fluid.

I did snap a picture of the fuel pump when I replaced it, looks like there is a separate vent tube? Never mind the greasy mess, that was penetration oil for the bed bolts that broke anyways:

 

Gas caps have not been Vented since EVAP systems were added to vehicles, so since the early 1970's

So whoever mentioned that must be very OLD, like me, to remember when gas caps were Vented, lol

Yes, 2002 should use a filler that looks like these: https://www.ranger-forums.com/attach...k-imag0885.jpg
A separate Vent hose to let the air out when filling the tank
It vents thru hole(s) around the filler tube, so vent is sealed when gas cap is on


Because you have replaced so many things it will be hard to diagnose the engine system
New parts are no longer tested by manufacturer, just made and shipped, they add a warranty to make YOU the FREE Quality Control Department to test all parts
So grain of salt, new does NOT mean "It Works"
New means "never test"

So if you swap in a new part and nothing changes, put back in the old part.........for now
Only sensors on an engine system that needs to be replaced are O2s, 100k miles or 12 years and they are done, used up

As for the 3,000RPM mentioned
All Computer run engines have a REV Limiter, usually set for 3,000rpm
Usually only enabled when an Automatic is in Park or Neutral, OR if Speedometer is under 5MPH
Computer uses sensors to detect Park or Neutral, and of course Speed
And computer itself could be the issue, stuck with REV Limiter on
I mention this because you mentioned 3,000rpm, if you had said 2,500 or 3,500 it wouldn't have trigger my response, lol

Computers also have a Speed Limiter, I think on our Rangers is was 90MPH or 95MPH, if it comes up

Not sure why the new gas cap helped either, EVAP system is an emissions system so heavily monitored, should have been at least 2 Trouble Codes if EVAP was leaking or pressure was too high