Ok I have a 1997 F-150 4.6. I have misfiring in 3 and 5. Recently before the misfires within the last 20,000 miles I have changed plugs (bosch 4+ crap) wires, o2 sensors, coil packs and fuel filter. Cant figure out this problem because I have replaced everything recently. Thanks for any help. Justin.

 

Hey, Justin. I would ditch those crappy bosch plugs and run some motorcraft plugs. I have seen the ceramic part of bosches crack numerouse times. Pull the plugs from the cylinders that are misfiring and check the plugs for cracks. Hope that helps.

 

Yes I know they are crap I popped #5 out and it looked fine. I got #5 code at first today erased put the plug back in go for a ride come back cel light on check the codes in I now have a #3 miss!

 

I popped #3 off too looks good.

 

I am having a similar problem. Truck started running rough and got a code #3 misfire. Pulled the plug and it looked good checked the wires and tested fine. Reassembled andit ran good for 3 days then ran rough and was hoping for #3 but got #2 misfire. Otherside of the block and different coil pack. I am going to start cheap and change the fuel filter. GOOD LUCK!!

 

Problem found bad accel coil pack with 6000 miles on it put a stock pack on and fired right up

 

The OBD on my '97 F-150 (4.6L) was intermittently reporting codes P0300, P0301, P0303, and P0305. If I cleared the codes, one or more would reappear within about 20 miles of driving (they seemed to randomly occur, but P0305 was the most common one).

I tried replacing the spark plugs, then the wires. While I was replacing the wires, I noticed that 1, 3 & 5 all attach to the passenger side coil pack. This seemed like a pretty big coincidence, so after verifying that the new wires did not solve the problem, I ordered a new coil.

The new coil solved the problem. I've now driven over 500 miles on the new coil without a single "check engine" light.

Not sure if this is a general solution to the "mis-fire" problem, but it's worth checking out.

 

My 98 4.6 showed a misfire on number seven. mechanic changed plugs. It ran good until it got hot I took it back and now he says he found that the misfire was caused by head crack or head gasket blow out. Does this sound plausible? Can some one tell me which one is number seven cylinder? Maybe I can pull the plug and search for anti-freeze myself.

 

No. 7 is the 3rd plug back from the front on the driver side. I would recommend taking the coil pak for that side off and have it checked at AZone.

 

AZ can check them ??? I asked my local one and they said they could check a standard coil, but not COPS...hmmm. Do you check them the same?

Also read on here a few times 'the dealer can do a stress test' (whatever that is) on them, but this is the first suggestion I've seen to have AZ check them out.

Maybe someone can at least describe the stress test for us mortals???

I have the 2 volume factory service manuals for mine and when I go to the testing cops section it says something like "see the service & testing manual available separately". My rant, why wouldn't that be in these zillion pages somewhere.

 

Sorry double post, computer puked on me.