I own a Ford Ranger 2.3L 4cyl with 87,000 miles. At 61,000 miles the engine began misfiring and backfiring at first startup of day, and also missing under load. The dealership replaced the coilpack and plugs which seemed to cure the problem. At 86,000 the truck again began missing ocassionally under load or mediu, m acceleration. It seems to idle fine and no symptoms are evident during rapid acceleration at higher RPMS. I have replaced the air filter and fuel filter which had no effect. Check Engine Light is NOT on. Any ideas would be appreciated!
Just to let everyone know what I found to be the problem. The engine has an aluminum head. As stated in my original post Cloninger Ford of Salisbury had replaced my coil pak and plugs 22,000 miles previously. When I went to remove the four plugs three of them came out without the need of a wrench. The white of the ceramic and the boots were literally covered with combustion carbon which had blown thru the threads of the loose plugs. This caused short circuiting and the misfiring. Evidently the mechanic failed to use a torque wrench and ended up not tightening the plugs sufficiently. I don't know if there is a moral but I ended up paying to fix a problem they created when they initially repaired the vehicle.