3.0 Surging RPMs

[aswormboy]

I have 1993 Ranger 4x4 3.0 auto. When Im driving normally it seems to be slightly down on power and at around 45mph the RPM constantly go up down. Its enough that I can hear it and barely see the tach move. Has anyone seen this before?

 

[c1skout]

It could be a vacuum leak, or exhaust, or a fuel filter. Check all the basics first (tune-up) and go from there.