Latest F150 problem

[CP]

I’ve been to 2 different repair shops now and both have struck out on fixing this problem.  1997 F150 4x4 – 4.6L.

Problem started towing the snowmobiles up Snoqualmie pass.  Before the trip I put in the “tow tune” from an Edge programmer which I’ve done many times before.  I stop at North Bend and fuel up.  All is fine until I get to Denny Creek then it starts missing, check engine light starts flashing. I check the fault codes and I have:

P0304 Cylinder #4 Misfire
P0232 Fuel Pump Secondary Circuit High

I stop, check the fuel pump fuse (it’s OK), swap the fuel pump relay with the horn relay, put the stock tune back with the programmer, and clear the codes.  Runs fine for a while after then it starts missing again but the fault codes do not return so I take it to repair shop #1.

Repair shop #1 – finds “the wrong air filter” is installed.  Replaces it with the correct air filter.  Problem returns almost immediately.  Off to repair shop #2.

Repair shop #2 doesn’t find anything.  They suggest I take it to the dealer for a complete tune, new plugs and wires.

Any suggestions on what to try next?

Is it possible that I just picked up some bad North Bend gas.   

[JDHasty]

One of the coils may have failed

[Woodchuck]

Move the ignition coil from cylinder 4 to another cylinder and see if the miss follows the coil. 

[andersonjk4]

Never had this issue in a pickup, but my 4-wheeler would do something similar.  Missing and sputtering and then run fine and then back to missing.  It turned out to be a fouled spark plug.  I would do what Woodchuck suggested to test the coil and then if coil is ruled out change the spark plug.   

[skeeter 20i]

I've used this website with some success in regards to trouble shooting and what to start fixing.  If I had to guess I would bet it's a COP what Woodchuck suggests is spot on with what I have done in the past to find out which one failed.  Hope it helps.

https://www.obd-codes.com/p0232

https://www.obd-codes.com/p0304

[Happy Gilmore]

First issue with my 98 was a fried spark plug wire. Then found a cracked spark plug throwing a off code because spark was shorting on the block.

[birddogdad]

 plug, wire, coil.. cheapest to most $ if you want to easter egg. .or do them all at once..

[eastsidemallard74]

Have you tried resetting your tuner, wee had almost a similar issue on our way to ND,reset and unplugged the tuner, went back to normal. There was a glitch with the tuner in our situation. Had to order a new one. Sms like everyone said above try swapping cilia to see if you get the miss fire elsewhere.

[jackelope]

Move the ignition coil from cylinder 4 to another cylinder and see if the miss follows the coil. 

I'm not positive, but I think that truck has 2 coil packs.  Not COP ignition.
You could swap coil packs and see if the miss follows the coil pack, but I also don't think that's going to set a fuel pump circuit code, and I don't think a fuel pump circuit issue will cause a misfire on 1 specific cylinder. I'm not a tech though.

The 5.4 has COP ignition, the 4.6 has 2 coils and plug wires.

[Woodchuck]

Move the ignition coil from cylinder 4 to another cylinder and see if the miss follows the coil. 

I'm not positive, but I think that truck has 2 coil packs.  Not COP ignition.
You could swap coil packs and see if the miss follows the coil pack, but I also don't think that's going to set a fuel pump circuit code, and I don't think a fuel pump circuit issue will cause a misfire on 1 specific cylinder. I'm not a tech though.

The 5.4 has COP ignition, the 4.6 has 2 coils and plug wires.

You are correct sir, I saw that after I posted but the coils do interchange and are easy to get to. Swapping them would still give a decent idea of where or where not to start. So I left it alone.

[j_h_nimrod]

That sounds similar to a bad plug wire I had, would run fine for a time and then start missing. Heavy throttle made it worse.  Had a COP do that in my 5.4, but as said by others no COPs in a 4.6.

Not sure of the fuel pump code though.

[Seahawk12]

Hopefully one of these guys are right.
I had a similar issue with my 150.
It ended up being my upper intake manifold.
I was able to do the swap out myself and did the coils, plugs and wires at the same time in my garage over a weekend for under $350.
It would be alot easier if it is just one of the coils. 
Good luck.

[follow maggie]

I used to have a 98 f150 4x4 with the 4.6  motor. It had this problem, among many many others, and the fix was reflahing the computer. One of the happiest days of my life was the day I dropped that POS at the auction and told them to sell it.