The truck starts good but it surges while it idles. Sometimes it cuts off after idling for 30 minutes or when I drive it for 10-15 minutes. I have checked the vacuum lines for leaks. Replaced the fuel pump, filter and all non-metal lines. All the sensors on the intake have been replaced. Still I have no luck with the surging idle.


I am rebuilding this truck not just throwing money at it. Every part I have changed is for failure. This truck sat in a field for 7 years and was given to me.

 

Sounds like a bad/ dirty IAC but, you said that you've replaced all sensors. Possible computer issue maybe? Try a junk dakota with an operable ECU if it doesn't help at least you've got a spare? my truck had the same issue after replacing the motor in it with a junkyard pull motor. sitting for 7years its bound to have leaks of all sorts double check those vac lines once more. what method are you using to check the lines?

 

have you checked your crankshaft position sensor?

This article seems to break surging down pretty well:
http://www.autoserviceprofessional.c...e-surge?Page=2

 

Truck has a new computer with the prom programed by local dodge dealer. Idle air controller is new.
I have not tried the crank position sensor.
I capped the vacuum lines one at a time and used my mighty vac to see if they hold a vacuum. I need to try the smoke machine with everything hooked up. I may have a small crack in a connector that I haven't found yet. Raining for the next few days so it will have to wait until then.

 

It wasn't the crank position sensor. Next I am going to try the vacuum lines

 

Did you check codes? It sounds like it could be a dirty EGR.
Is there oil in the intake? Could be a blown plenum gasket.

 

only code is for the water temp sensor. As for the intake I replaced the intake gasket and all seals when I got the truck due to a leak. I also put in a new EGR valve as the other one was clogged with who knows what.

 

Dude, Had the same problem on my 90 3.9 Dakota. Replaced all you did. Turns out to be the damb O2 sensor. Unpluged it an truck stopped surging. My truck only had one O2 sensor before the cat convertor. Some have them before and after so you may need to check both ii your truck has them. Replaced mine and motor runs great. Now I need a 4 speed O.D automatic trans. Hope this is of help to you...

 

My only other idea is Throttle Position Sensor.

 

Throttle position sensor was changed. Smoke checked the vacuum lines and no leaks.