I just changed my spark plugs in my 01 cherokee sport because it would start rough and misfire, now i start it this morning and i get a constant thumping noise comin from the engine that vibrates the whole truck and makes it run rough, if i drive really slow the thumps make it lose power like it will thump, the truck will slow down, then power back up, anyone know what it could be?

 

Did you put the plug wires back on in the incorrect order? Cap look ok? Is the thump seem like plug issue or is there knocking like a bearing or something?

 

You have the coil on plug rail, did you put it back on tight? If so, you may need a new coil

 

x2 what BP88 said about wires possibly being incorrect.. Not sure what engine you have, but here's a couple pics to check the order. Also, make sure you didn't break the wires. They can be easily damaged if you pull on the wires themselves.. always pull them by the boot.

 

Its an 0331 head if its a 2001, no plug wires

 

Did you double check the plug gap? What plugs did you use? These run best off of the cheap champion copper plugs.

 

It was the gaps, thanks for the help guys no more misfires

 

Awesome.

 

nd yeah i used the copper champions