Dodge Repair: high RPM IDLE

Question
Hi Roland,

I'm just following up on the high RPM idle.  Well I did the test and and nidle raised upabout half way, paused,  raised up almost all the way, paused. Then I turned it off.

It stopped raising once it warmed totally.  I think it may have something to do with the speed sensor since I noticed the milage numbers kept going up while the needle raised.  I actually sold it today but I'm still puzzed.  What do you think about the speed sensor?

Answer
I am confused. Initially you said the speedometer read high, then you said the needle went to 3500 rpm, so exactly which needle is not responding as it should?
What happens when you are simply driving the car? Does the rpm and the speedometer reading seem normal? If this is only a cold problem, I would forget for now. If there is a problem it will probably have logged a fault code in the memory of one of the modules (engine/trans/body).
I would get a fault code readout. Try turning the ignition key
"on-off-on-off-on and leave on" doing that in 5 seconds or less elapsed time. Then watch the odometer window to see the mileage reading change to show any 4-digit number preceded by a P. Let me know what you find. I would not change any parts without first doing a fault code readout. You have to identify what is the cause first.
If that doesn't produce a 4-digit number then go to a nationwide auto part store such as Autozone and get a free code readout using a plug-in reader. Or an independent shop will do a code readout for around $40.
Roland