Misfiring problem


New Member
Jul 19, 2021
I have a 1999 Jeep wrangler Sahara with the 4.0 in it. It started to misfire on me so I replaced all the ignition coil, plugs, and cables (one broke) but it is still missing. I’m doing my own research but hope you guys can help. If I take it on the road it spits and sputters but if I jump on the gas it gets up and goes, also if I’m barley cruising it drives fine (5 mph). Any help would be great, thinking possible fueling problem?
Double check the ignition wiring to insure that no wires are crossed/reversed. As careful as I try to be I got two wires reversed on my 97 TJ which produced the same problem. And it's not impossible that ignition wires could have been misrouted before you swapped the plugs.
I have heard of even when the ignition wires are installed on the proper plugs, but cheaply built wires are installed and routed parallel to each other a inductive field can periodically cause a misfire.
I experienced this problem years ago on a '69 Cougar XR7 with a 351W.
You can perform a test to see if this is the case.
In a dark area outside start the engine and look for sparks coming off the spark plug wires to ground or jumping between the wires.
I would also remove the distributor cap and look on the inside for thin lines in the cap which is referred to as carbon tracking... which will cause ignition spark arcing...