I'm new here and trying to help a friend with a 2003 Ranger with 5 speed. I've driven the car and at low engine speeds, such as between 1500-2000 rpm, there is an intermittent hesitation and reluctance to pick up smoothly. The result is a "hunting" sensation while trying to drive at a steady speed. The mileage is about 130k. Due to the age and mileage, is this engine likely to be happy shifting up at only about 1500 rpm, or does it need more revs to be higher on the torque curve? At higher rpm and at highway speed, there is almost no sensation of this hunting. My older Actron scanner has indicated no codes. The car gets good maintenance.

Based on age and mileage, are there any any suggested starting points for items to replace to improve this. Most tune up parts on the truck are maybe 5 years old, but under 20k miles on them.

Thanks for any advice!

 

Welcome to the forum

2001-2003 Ranger 2.3l DOHC Duratec's had IMRC(intake manifold runner control)
This was dropped in 2004 because of issues

IMRC is a good idea on paper, its like a mini-boost, but in practical applications it wasn't so good
The "runner" is the length of the intake tube from intake valve to throttle plate
When an intake valve closes air flow suddenly stops and that sends a pressure wave back into the "runner"/intake
The pressure wave then reflects back from the intake
At a certain RPM this returning pressure wave acts like a mini-boost forcing more air/fuel into the open intake valve
This return pressure has been known for many many years and why some carburetor intakes added more power are certain RPMs, designed runner length for maximum power at that engines best torque range, mini-boost

IMRC has flaps inside the intake runners that shorten the runner length and then lengthen it, so on paper there were TWO mini-boost RPMs, low RPM and high RPM

On a 2003 Ranger 2.3l I would check the vacuum system controlling the IMRC, the hoses could crack and leak so flaps weren't moving all the way closed or open
This WILL set codes if it gets bad enough, but not until then

It could also be dirty MAF sensor, clean it its easy

Throttle sensor(TPS) is a long shot but possible, if you can see Live Data from computer then with key on engine off, view the TPS data
16-19% throttle closed is spec
Then slowly push gas pedal down and watch % increase, you are looking for sudden drops or jumps in %
At foot to the floor WOT(wide open throttle) you should see 90%
It should never be 0% or 100%, ever
Should be a nice smooth up and down %

 

Wow, thanks for the comprehensive explanation and suggestions. I'll start with the IMRC hoses and also clean the MAF sensor. Thanks so much! Will report results when I can.