I had a similar experience which I eventually worked out resulted from using E10 Fuel (10% Ethanol) Once I returned to using standard Unleaded Petrol (ULP) the problem went away. CheersPAWheeler said:i have a 1999 tj with 4L. check engine light came on on the logging road. engine cuts out alot, more when hitting bumps. any ideas??. the code reader said cylinder 5 misfire. it gets alot worse when its cold and wet.