When I stop my pickup and put it in either neutral or park, the engine will rev from 1200-1400 back and forth for several minutes before returning to a constant normal idle rpm.

Why is this happening? It has just started on my 2001 Ram.

Air conditioner off, all fluids good, park and neutral yield same result.

 

My truck did that for a little while. Figuring it was due for a tune up i changed plugs wires cap and rotor. that settled it down a little but didn't completely fix it. So then i cleaned my IAC and throttle body and that completely fixed the problem.

 

Yeah, he's right. Take off your tb, remove the Idle Air Control Motor from the back of it, and clean the tb and the plunger and the hole it goes in with spray carb cleaner. Should fix it..........

 

Yeah sounds like a throttle body problem. Not sure how relevant this is but on my polaris virage (waverunner) It sometimes surges, in fact when i was cleaning it down in Panama City Beach fl Last week (spring break 06... more like ****-Fest 06) i was revving it to get the salt water out... Well in doing so the engine would surge to 5-6k on the tachometer and I had to kill the fuel switch just to shut it off. Found out later it was due to my dirty *** carberator and the fact that the f-in gasket between the Carb and the Intake manifold was shot... AGAIN (replaced 5th time in 3 years!!! 3 times by the dealer!)...

(Anyone interested in buying a 2004 polaris virage?? Lol!)

But yeah, definetly check the IAC sensor and clean the trottle body, I was reading somewhere on this forum about how the proper way to clean the trottle body is to actually take it off the intake. That way your not leaving gunk everywhere inside the intake. Do a search on it. =)

Just my 2 cents