My 4.0 has a bit of a low rpm stumble to it. Around 1,500-2,000 rpm under load the truck starts to buck/ stumble. I've cleaned the MAF, changed plugs/ wires, unhooked the EGR to test, and replaced an O2 that a scanner said was bad. Does anyone have any ideas on what it could be?

 

My first thought was plugs. But I take it none of those items you replaced changed anything?

If so I'd look for a vacuum leak or *maybe* the coil.

 

A/T or M/T, are you still running everything on that truck stock?

 

Nope...nothing really cleared it up.

Yes, the truck still has all of the stock accessories. It has 103k on it and it's a manual (just purchased from the original owner).

 

Have you looked into the tps check that w/ dvom on a slow opening koeo and see if there is a hesitation unless you have can use a scope or a vantage.