Have a 99 ford f150 with intermittent engine chatter . This only occurs when the engine is warm. This video took me 15 minutes of idling to finally get the noise to come . In the winter months it will take well over an hour to get it to make this noise. It increases a little bit with acceleration and in and out of gear until about 1500 rpms then it dissapears or I cant hear it anymore due to road noise. Any ideas what it is and how to fix ? Run 15-40 ha! Threw some lucas in it and it didn't help much. Has been doing this for 5k + miles seems like its mostly on passenger side or front of engine.

 

Anyone ?

 

Check the engine lifting hook, they like to loosen and rattle.

 

I'll look at it thank . Odd it only does it when it's warm .

 

Anyone else

 

Everyone else must be stumped as well!

 

Perhaps a stuck or lazy starter not getting clearance after disengaging, or a loose rocker arm/broken spring under the valve cover. I would look there first and see if anything looks out of place or worn out.

 

Thanks for the reply, Can i remove the valve covers without pulling the engine ?

 

It's tight in there, but you should be able to.

 

It was the alternator.... i cant believe it either but that was the cause.

 

Thanks for letting us know what the problem was. On my 70 Mustang V8, I had an alternator that hummed in drive and reverse before stepping on the gas when it went away. I almost got a transmission rebuilt under warranty because I, the shop foreman, and a couple of mechanics diagnosed it as the transmission. But, before they started they got an old timer mechanic to look at it and he found out it was the alternator.