i developed a heavy miss in my truck today. here's what i have checked so far, just replaced all sparkplugs this weekend. i started by unplugging the injectors. going down the pass side, unplugging one at a time 1,3,4 all had the same result. very noticable stumble at idle. when unplug #2 very small change in idle. i then checked voltage at plug and was 14+v. i am thinking the inj is bad. when driving the truck it seems fine till i get into it or hit a hill. also it is a 4.6 romeo with 126,000 on it. i prob managed to get some dirt in the inj when i pulled the fuel rail for plugs. anyone have any input

 

I would check the wire/COP first before getting a new injector. Because you cut off fuel, you also cut out any negative effects from the ignition. Many times after a plug change, a wire/COP can misfire due to the removal and install if new components are not used. Swap #2's wire/COP with another cylinder and see if the problem persists with the new cylinder.

*I used wire/COP because I don't know what year your truck is as the earlier models used wires while the later used COPs.

 

It doesn't necessarily mean it's the injector, just that it's that cylinder. If you've got wires, swap the two coils, they are the same part just pay close attention or maybe write down which wires went where. If the miss stays on the same cylinder swap two spark plug wires and see if it moves. Remember you have to swap both ends of the wire, just swapping it at the coil wont work. Maybe just buy a set of spark plug wires since yours are old anyway...

It's a lot easier if you've got COPs, just swap two and see if the miss moves. If after all that then it might be the injector.

Future reference, buy a 7mm chrome swivel socket and a 5/8" universal spark plug socket. You don't have to take the fuel rail off for a tune up at all.

 

Well now I look like a copycat.

 

I beat you by probably two seconds, I'll count that as equal if we're right
If we're wrong the blame goes fully on you because you were second


But really, does it matter? Great minds think alike I say.

 

sorry it's a 99, i have wires. and i put the wires on last summer. mon after work i will swap out two and see if i can get some more info. i never thought of that to check the coil. the reason i only changed the wires last summer, i was unemployed and was given the wires for free from a friend who sold his truck. this kinda blows cause i start my new job mon morning. luckily it happened today and not in the morning. one other thing, i actualy repulled that plug and it wasn't wet at all. i am still gana switch the coils mon night. i will post up what i come up with
i just grad from wyotech in the diesel field. i guess they unprogrammed my gas trouble shooting lol. and unfortunatley all my tools are at the new job. so i was working with a small assortment of tools.

 

new info, here is what i have. switched wires and coil's. same result. when it is cold it runs fine. as soon as the temp guage moves, and u get into the throttle, it starts to break up. it sounds like an old 2 stroke breaking up when the plug was loaded up. also there is no check engine light, and no codes. unfortunatley i cant get it to a garage, because by the time i get home from work they are closed.

 

Just a thought, you could have a plug wire that went bad, I had a motorcraft set
that lasted only about a week. It was my last thing to replace because they were like new ? who would of thought it ?

 

Remember you're not looking for the miss to go away you're trying to get it to move cylinders, then you can replace whatever made it move. Since all that is good move the injector and the miss should follow it.

 

ok i will move the injector wed night. any clue as to why as soon as the truck warms up it gets worse?