I have a 1990 Dodge Ram D-150 with the 5.2 engine.
The idle speed is ok at start up, but after it warms up the idle speed shoots up to over 2000 RPM.
I adjusted the stop on the solenoid which regulates how much the gas pedal is depressed and controls throttle at idle to no avail.
I have no "check engine" light on.
Any idea's.
Thanks.

 

Have you checked for a vacuum leak?

 

I checked the vacuum lines and they are ok.

What I found is that there is a solenoid on the drivers side of the carb which has a plunger that acts as a stop for the throttle linkage and it is defective.

I need to know the name of this part so I can order one.

Thanks.

 

ISC motor, or IAC motor.

 

Is the ISC motor the same as a idle stop solenoid ?

What I need has a plunger on one end that stops the throttle linkage and controls idle with 4 wire connector on other end.

 

Idle Speed Control, or Idle Air Control. My Ramcharger would surge at idle. Couldn't make up it's damned mind so i just unplugged it and set the idle at about 750 and forgot about it.

 

Sounds like a plan to me.
I did disconnect it and it made no difference but I don't know how to get the idle adjusted down.
I did adjust the plunger on the solenoid but could not get it to idle low enough.
The plunger is holding the linkage so the throttle is too far open.
Mine does not surge...idles fine when cold and increases as it warms up....gets up to around 3000 RPM.
I have left it parked until I figure this out.

 

Unplugged it when cold and still increases even if disconnected?

 

Yeah, it makes no difference if the ISC is unplugged or not; the idle still increases when it warms up.

 

OK, if you're 100% certain the throttle blades are closed, then it's getting air someplace and the computer is adding enough fuel to keep the mix half assed. When it's cold it runs on a pre-programmed rich mixture [open loop] until the o2 sensor gets hot enough to read,usually within a minute or so. Once it goes to closed loop the computer will read the o2 as lean and add fuel to compensate for extra air. TBI Chevies had a problem with TB base gskts sucking in but they ran fast all the time.

That being said,it should run like crap,or idle high cold instead of just warm if you have a plain old vacuum leak. Unplug the EGR valve and see what happens, as it only operates in closed loop. There should be no vacuum in the hose. Spray some Berryman's carb cleaner around it and see if you get a change in RPMs. It's possible the EGR has a combination of problems causing your malady. EGR opening when it shouldn't or leaking,and the air pump squirting air in the exhaust stream when it shouldn't. Pull the belt off the air pump too. Wild long shot I know.
Also spray along the edges of the intake manifold and around the base of the throttle body.