I have a 05 F150 5.4 3v with a cylinder 3 misfire only under load going uphill around 50 to 60 miles an hour.
I have new spark plugs new coil packs and I still get a cylinder 3 misfire like I said under load most of time just driving uphill I've never had the misfire happen while just driving through town it only happens under hard load. I also get a p0430 cat code for the driver side but my miss is on the passenger side. I don't want to just throw money at this vehicle in the economy right now I've thought about changing the injector the coil pack plug itself the catalytic converters or the fuel pump I have no idea if any of these things could cause or fix a misfire but I'm at a complete loss for why I'm getting this code." Maybe a bad follower is keeping the valve open" I could be driving up a hill and it feels like my transmission falls out I go from going 60 to hesitating to get to 40mph while my cel flashes.. This 5.4 is a pos it was "rebuilt" at 200k with new piston rings/ gaskets and timing done. Truck runs great even at idle and just driving around town but i can feel the power lacking 100% of the time just no cel till i drive up hill. I use reg 85 gas and change my oil 5-20 all the time. If someone could help me brainstorm some ideas id greatly appreciate it.

 

Have you swapped injectors ?

 

No not yet i can do it in a few hrs when the sun comes up. And report back. Is it the same as other cars just pull the pump relay and run the truck till it dies then pull the rail off and swap?

 

With fuel pump relay removed, I doubt it would empty fuel rail. Injectors don't work well gravity feed. Just get some shop towels or FAKE news paper (preferably the Huffing-puffington Post) and go at it.

But before you go there. Lets consult the PCM. So often, we should trust what it says. It is closest to any problem. You mention P0430. Do you have hard P0430 DTC. PCM says the UpStream / Downstream switch Ratio is below spec --- indicating the CAT isn't functioning normally. _IF_ thatt CAT is plugged up (restricting exhaust flow) it will cause the opposite bank to lean the fuel/air mixture out. (More of the intake air -as metered by common MAF- passes through and out the unrestricted bank.)

Also, I note that the engine is rebuilt. It could be something OTHER than the engine that wasn't addressed at that point. Would you be able to have the Bank 2 CAT checked out?

 

Relay is soldered on board . I just waited an hour after it was shutdown to let fuel pressure drop off .
Blow all dirt off around injectors so it doesn't fall in .Use motor oil on all orings to get them to seat easy after you clean holes with rag .
Did you replace boots on plugs they go bad with age ,heat ,chemicals -they may look good but to high voltage its another thing . Make sure plugs are torqued in 25-28 foot pounds ,look at plug to see if it was loose and getting blowby .
It may be prudent to replace fuel filter at this time . Are you having any trouble filling tank ,that can mean your vent off carbon cannister it starting to get plugged .
If you reused injectors after rebuild it very well could be past time to replace them all, they can hydro lock your engine and ruin it , they should be replaced in sets of four pcm controls them by the bank not individually . They are heavy duty cycle items 150k miles is enough wear on them . 05's were a defective year for injectors ,they extended the warranty for awhile but they would only replace a proven bad one.

 

Yeah the P0 430 I'm pretty sure the cats are bad when I hit it with the rubber mallet I could hear pieces of the honey comb bouncing around in it and im sure the injectors are old and never changed so ill swap injector 3 with 2 and go drive up some hills and see what happens. Now what ur saying about the driver side cat being clogged can cause the opposite bank "passenger" side to run lean? Wish i could just unbolt my y pipe and run it from the headers to see of thats the problem but i live in denver co and the cops would be up my *** in 2 mins.

 

And yes when I replaced my plugs and Boots everything look good the plug wasn't burnt or anyting just the electrode tip on the spark plug was damn near gone

 

I got that. I don't REALLY know a good simple red-neck method of checking for excess back pressure. But your mentioning hearing B-B's bounce in there when you 'rap' on it is concerning. You CAN remove Upstream O2's and drive briefly at the expense of O2 DTCs - and some significant noise. But it has to be bad enough to have driveability problems for that to show improvement in power. And that Bank 1 O2 is a B*#)!ch. Keep that Flashing CEL to a minimum, or you will melt the other one!

Second best method is a decent live data monitor scan tool. Fuel trims and O2 voltage graphs are excellent pointers. Fuel trims on the clogged side will be elevated, the unclogged side will be negative. But there can be other problems that exhibit themselves the same way.

 

What cheaper alternative for a live data scanner can I buy I just have a generic Edge tuner and it doesn't really do much. I'm going to go out and buy a injector and a fuel filter and just change them out to be safe it's a lot cheaper to buy an injector and a fuel filter than it is to pay $200+ for Diagnostics. Since i did the plug and boot a new injector and filter should help if it dont outright fix it. I just cant afford for some shop to have my truck for days and charge me tons for ideas not solutions." Im a roofer i work everyday" If this dont do it ill replace the cat and if thats not the misfire it is the p0430. If i still have a miss after all this ill open the valve cover and inspect followers. I don't let the p0303 happen much I don't know maybe once a week while driving up hills I just tried to avoid Hills as much as possible. Ill report back at the end of the day and see what we got

 

A "REAL GOOD" and very inexpensive live data option is Torque Pro ($5.00 App for Android), or Forscan (Lite is free) - and buy a Bluetooth dongle for ~ 25 -50 bucks. Torque Pro is a little more flexible (phone more convenient than computer). If you are not an Android guy - you can pick up an OLD Android phone for next to nothing. It does not need to be activated. Only have working WIFI and Bluetooth to download the app and connect to OBDII. There is lot of help on here for that if you're not too 'geeky'. You can get lots out of its basics - and will go way farther depending on effort to customize it.