Hey everyone!

Having an issue with my 98 Ranger 4.0 - and it's an odd one. I am noticing the truck will sputter only for a while after it's started up. And it's not when it's just started either (thought at first that it was a cold-only thing). Even if I drive the truck around for a while and then park it and shut it off, it will sputter for a good while when I go to drive it again (it clears up if I rev it a bit). Truck has new plugs, wires, air filter and recently had a fuel system, crank and cam-shaft sensor replacement. Also, it appears to have a new IAC valve.

What do you guys think could be my issue here? Thanks!

 

Welcome to the forum

Cycle key on and off 3 times before starting
Key on, count to 2, key off, repeat 3 times

This will pump up fuel pressure in the system, in case it was lost.

next test
turn key on
Push gas pedal down to the floor and hold it down all the way, this SHUTS OFF fuel injectors, this is called "clear flooded engine routine"
keep pressing down on the gas pedal and turn key to START
Engine should turn over but not fire or startup, if it does you have a leaking fuel injector

As soon as you release gas pedal fuel injectors will start working
I do this every morning when I start my 300+k 4.0l OHV, I like to get oil pumped up and around the engine before starting it


And remember..............
"New" used to mean "tested and works"
"New" now means "you test it for us and we will replace it if it doesn't work"

So "new" parts just means no one ever tested them before, you hope it works, but never assume it works


Also what did the old spark plugs look like?

Older engines get leaking Valve Guide seals, so each time you start the engine cold or warm there will be extra oil on the intake valve stems that has to be burned off or sent out exhaust with a mis-fire before engine can run smoothly

A working PCV Valve/system helps reduce oil leaking down valve stems