engine flutter noise?

[silver surfer13]

going down the road..esp under a load like having a/c on..i will hear a fluttering sound in engine..like bad gas or spark knock sound....the exp is drivin like a granny owns it...hardly over 55mph...no stepping on it to pass someone for 90k miles ....does that have something to do with it? bad gas?..maybe a valve adjustment...help?.s 2001 4.0 v6 4x4 explorer...

 

[manaen]

you cannot adjust the valves on these engines that use hudraulic lifter that are self adjusting.

when was the last time the engine was tuned up Plugs, Wires, Air filter, Fuel Filter, Clean IAC, Clean MAF, Run FI cleaner, and Seafoam through it.


You could also have a vacuum leak, or clogged CATS, or a fuel pressure problem

Start with the tune up if that doesnt fix it then run a vacuum test to make sure there are no leaks in the intake or clogged CATS and do a fuel pressure test to see if you have proper fuel pressure at the fuel rail.