Engine “hunting” or “surging” at idle or low speeds can be caused by various factors. A common culprit could be a vacuum leak or an issue with the idle air control valve. The vacuum leak can cause an imbalance in the air-fuel mixture, leading to unstable engine idling. Similarly, if the idle air control valve, which manages the engine’s idle speed, is malfunctioning, it could lead to surging.
Another potential cause could be issues with the fuel delivery system. If there’s a problem with the fuel pump, injectors, or filter, it could result in an inconsistent fuel supply, causing the engine to surge.
It might be best for you to take your truck to a professional mechanic to accurately diagnose and address this issue. Stay safe on the roads, Tom!