My check engine light came on in my 98 f150(4.6)so I stopped by autozone and had them check the code. It said the #3 cylinder was misfiring. The truck had been skipping anytime under load. Should I replace the plug first then try the wire then the coil pack? That should be all that would cause it to misfire right? Which cylinder is #3?
Its got 86k miles on it and I had the plugs and wires changed about 15k miles ago. I also had to replace the idle air control valve last week. It was skipping before replacing the iacv but I did notice it worse after.

 

#3 is the third from front of engine on passenger side. See diagram below.

4 8
3 7
2 6
1 5

 

Thanks. I will try and change the plug and wire this weekend. Will the misfire code include the coil pack or is that a seperate code?

 

Misfires can be:
1. Plugs
2.Wires
3. Coil Pack
4. Fuel Injectors
5. Bent or stuck valves
6. Worn rings

Chances are very good that it's only the plug, wire, or coil pack. Slightly less that it's the injector. Remotely that it's the valves or rings. Good luck.

 

yah man i am new at this i just signed up but about ur miss fire it could also be your cam shaft sencer i just did that to mine and it was skipping 2 threw fifth gear. does it feel sort of like it is about to stall then catches?

 

He has a single cylinder misfire code. No way it can be a cam sensor.

If, on the other hand, it was bucking, difficult to start, or otherwise acting a bit retarded, then the cam sensor would be a likely suspect.

The output of the cam sensor is used to synchronize the injectors to the spark. When it fails, it affects all cylinders.

Steve

 

It only misses under load. If I am at a low rpm and give it a lot of gas without dropping a gear it does it bad or going up a hill. Idling or driving a set speed. say 60 mph, it doesnt do it. I am work today so I will pick up a plug and try that first and work my way back. Do the auto stores sell a single replacement spark plg wire or do you have to buy the whole set? I just had them replaced about 15k milea ago and see no need in replacing them all.

 

I don't know if they sell just a single but i am pretty sure they don't. If i was you i would put all new ones in there so the other plugs won't go out at differant times if you know what i mean. But yah mine does that same exact thing except i haven't caried a load yet because i just put a new clutch in mine and i don't want to do anything like that yet until i get about 500 miles to break the clutch in.

ROSS

 

Autozone sales single but wouldnt sell me a plug without knowing what was in it now. A shop changed them and I dont know what they used. I will pull it out when i get home tomorrow. I am also going to change the rear end oil I believe.

 

I had a cylinder 7 misfire, truck bucked when accelerator was pressed, if you just go one speed drove fine, i replaced the plug problem stopped, then it died at the stop lights, and started idleing funny , i checked the vacuums and it now does the bucking under acelleration again,....

 

my truck was in at ford getting other work done to it they happen to pick up a code #3 miss fire. ford told me to replace spark plug rubber boot. fixed the problem.