New member here. I own a 2001 Silverado with 223,000 miles. I LOVE this truck. A whistling started a couple days ago. It goes up and down as I press and release gas pedal. Any ideas? It is very hard to hear when engine is in Park or not moving.

 

I would check the air ducting starting from the air box back to the MAF sensor just to see if maybe something go stuck in there and then I'd clean the MAF sensor.

When was the last time you had the belt replaced? May want to try that also.

 

I cleaned the MAF sensor a couple weeks ago. Would a serpentine belt make a whistling noise? I can't hear it when I open the hood, only when I'm driving.

 

Well a belt usually makes more of a squeaky sound and you'd definitely hear it with the hood open, just an idea.

 

Truck was rough starting today and would not maintain a cold start high idle. I saw a video about checking for intake manifold leaks today. Would this type of leak change as the truck accelerates and decelerates. Noticed the whistle lowers in tone as car slows down and raises in tone as car increases speed.

 

Started truck this morning and it held its idle but service engine soon was flashing. Put it in gear and instrument panel went wacko. Lights flashing, gauges bouncing, odometer flashing. Guess I'm headed to the shop.