Folks, I need URGENT HELP concerning my 1989 DODGE POWER RAM "W100" truck (5.2L, 318 c.i. EFI Throttle body with auto trans).

At cold startup, the engine idles nicely for about 20-30 seconds then begins to idle roughly with frequent episodes of a momentary idle drop to near stall. Most of the time it will catch itself and bump back up to normal idle rpm (still rough) repeating the sequence ...but will occassionally stall out....Never a surge upward in idle telling me that a vacuum leak is probably not the issue....And, if you give it a little gas and hold the gas pedal there, it runs OK. Only issues are when it drops back to normal idle rpm.

Here is what I've done so far:

1. Rebuilt / cleaned Throttle body with new gaskets and new O-rings for the fuel injectors.
2. New plugs, wires, distributor cap and rotor button, and new ignition pickup in the distributor cap.
3. New Idle control solenoid (adjacent to throttle body)
4. New fuel filter
5. New Air filter and PCV valve
6. New O2 sensor.
7. New Fuel Sending Unit (pump) in the gas tank.

Also tested the MAP SENSOR (functions properly) and inspected almost all vacuum lines for leaks (none)....Looks like a new EGR valve has been recently installed.
Viewed the fuel injection into the throttle body barrels while idling. Fuel sprayed evenly into the barrels even
just before the idle dropped and stalled the engine (telling me that a lack of fuel flow may not be the issue).

Ran a "key on-key off" code check and got #37 which indicates:

part throttle lock/unlock solenoid driver circuit (87-89 models) OR, solenoid coil circuit (85-89 Turbo I-IV models).

Wonder if the THROTTLE POSITION SENSOR could be an issue??....I would think that the FUEL SENDING UNIT in the gas tank
may also be an issue but, as mentioned above, I just replaced it.

Again, the truck cranks easily and idles nicely for about 20-30++ seconds at cold startup then begins idling a little rough with abrupt, frequent drops in the idle rpm (almost near stall with an occasional stall). It could still be fuel injector issues because I just don't know enough to be completely accurate.

And, does anybody think the Coolant Temp Sensor could be an issue??

All help, opinions are greatly appreciated!!!

Mike

 

Check your TPS for nice smooth operation and for varable resistance that's smooth with no drop offs in it.
Yes - coolant temp sender can cause these issues and even though the egr valve looks new make sure its hooked up to the correct tap with all the delays working and the correct valve.