I have a 2007 F-150 XL Triton 4.6 liter that is running lean in bank 2 on cylinder 5 which is causing a misfire. It has 311k miles. I have change the spark plug, coil pack, CPS, PCV Valve, fuel filter, did a top engine clean and an intake clean. It is much better but still running a little lean and still causing a misfire. Sometimes it moves to cylinder 4 or 6. What am I missing?
Maybe instead of considering if the lean condition is causing the misfire, consider if the misfire is causing the lean condition.
When a misfire occurs not all of the oxygen (O2) is used up during combustion (misfire is incomplete combustion). Then that "unused" O2 is sent through the exhaust and the O2 sensor picks up that high level of O2 in the exhaust (because O2 and A/F sensors can only read O2 levels) and the computer simply says that there's too much O2 in the exhaust ((it's right)) and adjusts fuel trims if it's correctable or sets a "lean code" if it isn't.
Your engine has 311,000 miles ((impressive)) but like @imperator says you have to start your troubleshooting by doing a compression test with that kind of mileage.
As far as a vacuum leak, look at your fuel trims during idle and then again while holding rpms at around 2500 rpm for a minute or two.
If it's a vacuum leak the short term fuel trim will start going down while holding the high rpms. It may even start pulling the long term fuel trim down.
You say that Bank 2 is running lean. What do the Bank 1 fuel trims look like?
If you look at the Freeze Frame data, are the misfire codes being set during any particular condition? Like at idle, or cold engine, or under load, or at lower or higher rpms?
Also your misfire codes are bouncing around between cylinders 5,6, and 4. But it may be relevant that the firing order is:
1-3-7-2-6-5-4-8.
So maybe don't suspect the coils or injectors because 3 failures on 3 cylinders (even intermittently) at once is nearly impossible.
If the compression is good and the positive fuel trims persist at all rpms maybe unplug both VCT solenoids and go for a slow drive. See if it still misfires. You'll lack power and you'll probably set circuit codes but go easy and see if the misfire(s) goes away.
If they do then change your oil and your VCT solenoids
The pil change was done 2 weeks before the misfire started.
Errr oil not pil
I'm not seeing any VCT Solenoids on this engine at all.
Please don't use vulgar language here. Family friendly forum. Rules are posted on the front page for your convenience. Thank you.
Sorry about that but it is marked a private question, so technically no one else should be able to see it but Myself and y'all.
nothing about private questions in the rules. Next infraction will be an instant removal from the site.
Thank you.
Fair enough. So how about My question?
I answered it below. Scroll down.
Sorry I'm new here and didn't see the response til now. Thank you.
Please try the misfire troubleshooting in our FAQ, and see if anything there helps. It's sounding like a gasket issue, so start with smoke test and compression test. Especially with your high mileage.
Smoke test was negative. No smoke came out the engine what so ever after 25 minutes of smoke.
the smoke could come out of anywhere there's vacuum. Not just the engine block. various hoses and reservoirs, hvac system, brake booster, evap lines heading off to the fuel tank, ...
While you have the smoke machine, use it to check for exhaust leaks.
And the compression test?
And if that's not it, then maybe there's bad fuel injectors. An injector balance test using a professional diagnostic tool can reveal that.
I'd try moving the fuel injectors on the problem cylinders and see if the misfire follows.
Ok. I'll try that.
I'm not seeing any VCT Solenoids on this engine at all.
Rockauto.com lists them for the 2007 F-150 with 4.6 V8 engine.
I get that. Everyone list the exact fit part and all but I can not locate them on the engine anywhere.
I'm not sure what happened but about half way to work all of a sudden the misfire stopped and all power and gas mileage is restored. Who knows maybe the truck is possessed. But it is still running great as of today. I'm totally lost on this one. Misfires don't just fix themselves!!!