I have a 1998 Ranger with a 2.5L 5 speed tranny. My problem is while the clutch pedal is pressed in during shifting (foot off of accelerator) the engine rpms never decrease. IAC valve has been changed,no codes thrown. Any help is appreciated.

 

Vacuum leak somewhere.

 

This is a normal "dashpot" function of the IAC motor. The engine will retain its RPM during shifts to reduce emissions.

A dashpot is a mechanical device, a damper which resists motion via viscous friction. The resulting force is proportional to the velocity, but acts in the opposite direction, slowing the motion and absorbing energy. It is commonly used in conjunction with a spring (which acts to resist displacement).

 

a bad pcv valve will cause high revs in between shifts and will not throw a code.

 

If you want to determine if it's the "dashpot function" or another problem, you can disconnect your VSS sensor in your dash. Can't remember what color wire it is. But if you do it right, your speedo wont work either. The GEM won't think you are moving so the motor decreases RPM immediately. I found this out while recalibrating my speedo.

 

I've noticed mine will do that if i have the a/c on. But the rpms drop when i do'nt. Not sure if thats the norm or not just norm for my truck.

 

Thanks for all the help.Found the pcv valve dislodged from oil separator.Problem rectified!!

 

glad you got it sorted out

 

Could you post a PIC , where to find the PCV valve, my ranger 97 , had the same problem.
Thanks in advance

 

the pcv valve is directly underneath the intake manifold driver's side of engine
just look and you will see it.

 

Mine has been doing the same thing.. Also missing a little bit, i will have to check this when i get home