hi , truck has a surging idle , when running around 1100 - 1400 rpms the idle wil surge up and down , below 1100 its fine above 1500 its fine . any ideas whats causing this .

 

Any codes? Several things come to mind. Most will set codes. Turn key from off to on 3 times ending in the on position. Codes will read off in the odo screen.

 

Turn off your power puck and then see if it still does it.

 

pulled codes p0602, p0633 one is for running programer and other is for security key , why would the puck be causing it its been on there for awhile and this is only a new problem .

 

Maybe a dirty or bad FCA.Do a SEARCH on it.

 

That was my next guess Hounddog. I just can't fathom why only at a particular rpm's. The puck could be causing a problem.....they can go bad. Also try recalibrating the apps. IIRC, you unhook the batteries, set for 10 minutes or so, re hook them up and with the key on/engine off press the accelerator slowly to the floor and back. See if it makes a difference at least.

 

Almost forgot.One way to see if its a sticking FCA is add a pint or two of the ashless two stroke oil to the fuel.If its sticking it will clear up some time during that tank of fuel.Once its gone and filled back up it will start surging again.That trick works.

 

it does not do it all the time , it will do it one day , then not for a few , it seems to do it more after running on the highway for awhile at constant speed then when you get off and are just running around 30 - 40 at 1100 - 1400 rpm it will do it

 

That also can be one of the "side effects" of programmers and boxes. That is right where the power band kicks in as well. It never did it before ? or never noticed it before?