Over the past few weeks, the engine on my '97 F250 (33K miles) has been making a new and different sound when accelerating.
It sounds like "chig-a-chig-a-chig-a" but only does this when accelerating.

Is this normal and possibly just die to the recent warmer weather?

thanks.

 

Is it a high pitched sound? More like a ting-ting-ting? If so, you probably have a pinging engine. Try a tank of high octane fuel. If the sound stops, buy a bottle of Chevron Techron and follow the instructions and use your regular fuel. If the pinging stops, it was carbon build-up. Plan on changing your oil. Bet it turns black after treatment. That's the carbon blowing by the rings and down into the crankcase.

 

It's not a pinging sound. I ahd already tried the hi-octane but it had no effect on the sound. thanks.