I have a 1986 f150 5.0 auto, that started to miss, and has gotten worse. I replaced the plug, they looked to be in great shape, but I replaced anyway, I know I need to replace the wires going to do that this weekend, cap and button too, my biggest question is. Is their any fuel problems with these trucks? is their anything else I should check. Thanks

 

You are starting with the basics.. Check it for vacuum leaks too. That will cause an engine to do crazy stuff.

 

Welcome to the board!

You are on the right track, just do as NGM says and you will be fine, I think.

 

Thanks for the info guys I will update yall this weekend and also try to get some picks shes ugly but I like her.......

 

welcome

 

Start with the basics. Isolate (which cylinder). If compression is OK, check for spark, listen for injector pulse. If miss is at idle only and runs OK at high RPM, check for vaccuum leak. Now if still can't determine what the problem is pull the valve cover off. Make sure the valve push rods are in place. Back in those days, we would drop a push rod and have no valve operation. Exhaust valves =dead miss with possible backfire in intake. Intake valve = dead miss perhaps a slightly lower compression reading. Hope this helps, and good luck.

 

The miss is not bad at idle but gets worse when you get on the gas, last night comming home from work when it shifted into 3rd the miss didnt go away but seemed to be better weird. but it was still there, im going to look for vac leaks today let yall know what i find, also the motor is not the org. the block and heads ar from a mustang, the org. motor blew, at least the guy I got it from told me? but still a 302 is a 302 right?

 

ok replaced the wires cap rotor, checked for vac leaks all is good, the miss is still there, its the same if its hot or cold HELP!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

OK, again lets isolate the miss as to which cylinder. You said you replaced cap and rotor. Loosen all wires at distributor. Just leave then loose in the distributor cap. This way you are able to lift then off one at a time while the engine is running. Start engine and one at a time remove a wire and listen for the engine to begin to miss more. The plug wire that does not change the way the engine is running is the cylinder that is missing. Follow that wire down to the spark plug. You can pull the wires off the plugs one at a time but I find its easier working at the distributor cap. If this locates which cylinder is missing, swap spark plugs with another cylinder. Repeat test if its the same cylinder, then with that wire disconnected, start engine and see if their is spark at the disconnected wire. Place a screwdriver into end of wire and place metal shank of screwdriver near metal on the engine. (Exhaust bolt) If spark is present (should be blueish in color) then using a long screwdriver, a dowel rod or even a piece of rubber hose, touch the injector and listen at the other end of the stick, hose or what ever for the injector noise. Comepare to a know good firing cylinder. If all this is understandable or better yet just call me 702-297-1620.

 

Welcome to the forum!