I have a slight miss at lower RPM's,nothing shows up on the Jeep's Comp....Changed plugs,they were shot but didn't help the miss,,,any ideas ?.I know if I take it to the dealer it will be trial and error at my cost.

 

Did you try pulling a code yet ?

 

A true engine misfire WILL set a code on the OBD II diagnostic system. A dirty air filter, crappy fuel, etc that is causing slight roughness will not....check air filter, change fuel supplier. One other thing- take it out and run the hell out of it for a bit, you might see a big difference.

 

Check the plug wires by the powerpack, sometimes the one closest to the alternator support bracket get's turned to close and will arc to it causing a slight stumble @ idel.

 

The computer detects a misfire by seeing a slight drop in engine speed during the next 120° of rotation after it tells each plug to fire. That's how it knows which cylinder is misfiring.
There is a threshold for throwing a code. It is possible for an observer to perceive a slight misfire (or roughness) for which the computer will not turn on the light.

 

I have had it at the dealer,they say no codes,changed plugs,they were shot but the wires look good,what do you all thinjk about doing that injector cleaning process??

 

Back in the days of leaded fuel and low energy ignition systems a rough idle was sometimes caused by a valve seat with a little carbon buildup. When all else failed you could run the crap out of the vehicle and it would blow these valve deposits out of the engine. Same with a preignition or run-on problem, carbon buildup on the pistons would get hot and glow enough to ignite the fuel in the cylinder. A coke bottle full of water trickled into the carb at a fast idle would clean the piston tops like a sandblaster. No carbon no misfire. AHH the old days....

 

Yeah, I miss those days, too.