I've got a problem with my truck. Battery was going bad, so I replaced it. Afterwards, the truck started idling funny...like it was hunting for a certain RPM. Got check engine light and the code reads "P0506 Idle Air Control, System RPM Lower Than Expected". Replaced the fuel filter, checked for vacuum leak, cleaned the air filter, replaced the throttle position sensor, all with no effect. Truck is 2004, 4.6L, 2WD. If the engine is idling, say moving through parking lot and I turn the steering wheel, engine dies sometimes. The only code I've gotten is the low idle speed.
Hope someone can help out on what to do next!
Thanks

 

I know that you said the idle surge started after a battery change, but maybe it's a coincidence. The Idle Air Control valve on side of throttle body can cause a surging idle if the IAC has a build-up of carbon. It can be cleaned or replaced but if you intend to clean it, be careful not to damage the protective coating in the bore of the throttle body. Carb / Intake cleaner should have a notice on label stating it is safe to use on injected engines (O2 sensors) and coated Throttle bodies. A good cleaning and drying may help the idle suge. Good luck