2010 f150 fx4 42,000 miles if i am driving around 20-30 mph and go to accelerate sometimes it sounds like a diesel idling. Anyone have similar problem? Doesn't do it all the time. Noticed it today since it is 85 degrees out.

 

Thinking it may be the cam phasers sounds happens around 1500rpm then goes away if I rev it up higher.

 

Cam phasers or spark knock. Try some premium gas and see if it quiets down.

 

I am guessing can phasers cuz if never did it before till today when it is the hottest it's been all year yet

 

Update.
Truck didn't make noise going home from work when it was 65 out. Today on way into work about a 35 mile highway drive. Get to work and cane hear the sound between 800-1100rpm. It's 85 degrees outside. Notice it when pulling away from a stop sign driving through those rpms. Goes away once over 1100rpm. Sounds like a knock/clatter like a diesel knock. From inside can sounds like it's coming from passenger side.

 

Update 2:
Starting to think may be the tune I have. Maybe a spark knock. Going to put back to stock and see what it does then.

 

Try using a higher octane if it's spark knock.

 

New air filter and 89 octane and it seems to went away.