I was coming home from work this morning and was about five miles from work 50 MPH on country roads when the engine got weak and rough. Check engine light started flashing. Kept going (no place to pull off), about two miles later got a backfire (sounded more like going into intake then exhaust). Check engine light went solid. Got home, pulled out my tuner to check codes. Only got one code P0305 (misfire on #5 cylinder). Cleared the code and restarted engine. No more check engine light and truck running almost normal. Even after a short test drive to video store and back.

Truck has felt like it has had a very light misfire for a month or so. No codes before today and have not been able to find anything.

Any ideas as what can be the problem? Currently running stock program (not tuned) and on regular fuel. 110K on truck, 10K on sparks, almost 30K on wires and coil packs and injectors are original. Oil changes every 2500 miles, trans flush every 30K, etc.

How do you test injectors, coil packs, and anything else it could be?

Thanks for your help.

 

I would go to cylinder number five and check the spark plug well for moisture. Have you washed the engine lately? If it were a stuck injector, it would not have cleared itself up.

Good luck,
Doc

 

Haven't washed the engine. No rain or snow in past few days. Engine is dry. Code cleared, ran a few miles OK. Restarted truck and code came back and truck is running rough again. Bought new plugs, will put them in tomorrow during the day. Wires look OK no burns or anything.

 

I experienced the same problem with my 97 with 4.6l. The first time I had all plugs changed and everything was all ok for 3 weeks then prob reoccured. Never used Motorcraft plugs and from this forum I think may be cause. Will change after I change 2 new manifolds ( both cracked). Have you found anything new since last post? Does anybody know of an economical source for manifolds?

 

Changed plugs and wires. Plug was OK, it was the wire that was corroded. Found anti-freeze in plug hole. Truck has been running good past few weeks without a hitch.

Figured out anti-freeze came from when son changed upper radiator hose in his Auto Shop class at Community College. Had him change the trans filter too and it cost me. I took the trans pan gasket it out of the box so it wouldn't get used (reuse the pan gasket that is there - it's even states it on the pan). The instructor had him order a new cork gasket and throw the factory installed one away. Had to take truck to trans shop for leaking trans seal and the cork gasket was leaking to. Changed it again with the right one. Live and learn.