I have a 2007 f150 with a 5.4 that's giving me fits. Recently deleted the cats and did the plug foulers after one of my cats went to crap. Truck runs great but still throwing a 0420 code and will slightly misfire under a hard acceleration .it has an edge performance programmer and k&n CAI. Had to get a special tune for the CAI to work nicely with the programmer if I wanted to run 87 octane but runs great. Here's my question...could a vacuum leak or shot plug or coil or injector cause this code and misfire to occur? It's only on bank 1 so it's gotta be isolated to that side and it's not showing a misfire code and only does it when it's under heavy acceleration. Checked the map sensor and it's good and clean and pcv looks good too.

 

How many miles on the spark plugs?

 

They were all replaced with OEM plugs when I bought the truck with 95k miles. Has 170k now. Would be nice if it's just time for plugs again

 

Well no major changes yet. I replaced the fuel filter which I'm sure need it done anyways, and just replaced the elbow and hose for the PCV valve. Thought I may had some kind of vacuum leak. The truck still hesitates and misses under heavy acceleration though. It will still show a code of 0420 and I know what it means but I don't have any catalytic converters in the truck right now. I put a straight pipe in for each cat and then welded in 02 foulers for the downstream oxygen sensors. Not sure why only one bank would show that it is below threshold though

 

Time for new plugs, and you may have some weak coils. Plugs on a 3V should be changed every 60k.

 

Well, the P0420 code is there because the cat is missing and the anti-fouler(s) you installed are inadequate to fool the computer. That's a different issue from the misfire so treat them separately. Most likely, the failed cat was due to leaving the misfire unresolved for too long in the first place.

Fix the misfire first then come back to the P0420 if it still is present. You may have to stack another fouler with a smaller hole to increase the O2 sensor's setback from the exhaust stream to get it to work as intended.

 

Thanks for the replies. Doing new plugs and cop today. Fingers crossed that's the ploblem with the misfire. Good idea on adding another fouler too. For as cheap as those things are I may as well try that too. I'll report back

 

Just got word from the garage I took the truck to today and seems the cops are fine. Not too sold on that though. Since I only get a misfire/backfire under heavy acceleration, there's no way to check the could under that type of load. Only static testing. Any other ideas?

 

Did they change the plugs?

 

No they didn't yet because I don't have $600 to drop on it now. Going to just drive it easy for a couple weeks and do it at the end of the month. Very frustrating

 

$600 to change the plugs is pretty excessive. Should be about half that price, and if they were replaced properly before and are removed properly, they shouldn't break.