How do I diagnose vacuum problems on a Ford F150?

Answer by  worker8388 (994)

Test the vacuum reading at idle speed,it will diagnose burned valved sets or leak in gasket. Make a test at 2000 rpm to know weak valve springs. Testing at higher speeds will show the details of burned valves or ignition misfire.

Answer by  heather88 (1897)

You would need to take it in to see what is wrong with it. They would know what to do for it. Or you could get a manual on the truck. They will be able to help you out. But your best bet is to take it in to the shop for repair.