So I have a 97 4.2 that has not given me one day of good running service since I bought it one year ago. Something always goes wrong. I have been battling a major misfire problem for about 5 months and am having no success, please please please help me!!
The misfires seem to come most often under acceleration (but sometimes while cruising)
My OBDII scanner says misfires are on Cyl #1

I have replaced
Coil (OEM)
Plug wires (OEM)
Plugs (autolite premium)
Rebuilt heads (mine were cracked)
Upper engine gaskets (heads and up) (Viktor)
Exhaust manifold (OEM)
O2 sensor (NTK)

I also have code P0420 ( Bank #2 Catalytic below threshold)

Ready to blow this truck up pretty soon... Please help me.
I really do love F150's but this one has it out for me...

 

Serrrrrriously people. Please, throw me any idea! I will try it. I do not want to get rid of my truck because of this problem.

 

Here are a few random ideas without seeing the truck:

Leaky valve covers? I have seen this on another vehicle where the spark was literally jumping to the heads before getting to the plugs.

Any crossed/cut wires?

Clogged injector? Replaced fuel filter regularly?

Good compression in all cylinders?

 

There is good compression.
Changed plugs and wires therefore no arcing.
I think I will test the injector and inspect/ test fuel pump/ filter

 

On my 99 4.2 i had the same issue... brought it to ford and it was the plugs... ended up with the cheapies and the truck ran great... just a thought you may want to try, the reason was allegedly the aftermarket plugs i put in didnt have enough resistance and thus were missfiring.... cheapest copper plugs fixed the issue and since then i always buy OEM plugs from the stealership

 

I will look into that because mine has autolite plugs

 

yeah it only started on mine after the plug change... i cant remember what the exact symptoms were as it was nearly 10 years ago but worth a try....