Gentlemen,
Like so many of you on here, I too have the classic Ford F150 5.4 misfire.
In the past, I have been able to attach my code reader, receive a code like "Misfire on cylinder 2", replace the coil, and everything was good.
This time I wasn't getting any codes, even though the engine light would occasionally flash, then go out.
Last night the engine light finally came on and stayed on. I expected to attach my reader and find out what coil to replace, but instead I got the code: P0174 System too lean Bank 2.
What do I do with this? Could this be causing the misfire symptoms or do I have 2 separate problems?
Any tips or advice is greatly appreciated.
Thank you in advance, Joe


FYI: My truck is 2004 F150 XLT 4x4 5.4L with 204,000 miles

 

Likely your misfire is causing the lean code. Any past service? Plugs? Coils? Boots? I have fixed all of my last misfires with simply replacing the boots. OEM coils rarely go bad. I use Torque Pro to read live data and I can run a mode 6 test to see how many misfires each cylinder has and this is how I have pinpointed which one(s) to concentrate on. You can either work on all of them or find a way to read live data and figure out which one is misfiring.

 

I replaced all the plugs around the 100,000 mile mark, so I'm due.
I've replaced several of the coils as they've gone bad. I'll try replacing the boots and see how that works. Do you recommend any specific brand?

 

Any boot that is OEM quality. When I do mine I usually replace all the boots and springs. Cost is about $40 in my area for a set of 8 springs and boots together. Remove the coil (now is a good time to blow out the plug well with compressed air, this gives any moisture from the compressed air time to dry while your doing the other work) and pull of the old boot and spring. Clean the point where the spring attaches to the coil with some electrical contact cleaner. Put the new spring on making sure to get good contact. Then put a little dielectric grease around the coil where the boot will be so as to seal out moisture. It doesnt take much grease and you dont want too much because it does not conduct electricity and could cause another misfire. Then put a very small amount of dielectric grease around the inside of the boot where it will contact the spark plug be careful not to get it on the spring as you dont want to interrupt the the contact between the spring and the plug. Then carefully replace the whole assembly avoiding getting dirt in the end of the boot. This is my process that has worked numerous times!

 

These were the exact ones I used on my truck. https://www.oreillyauto.com/detail/u...coil+insulator

 

I fixed that on my 2003 4.2 liter V6 by cleaning the MAF. Just broke open the air inlet and hosed it down, then put it back together. I think that the PO before the PO had a K&N filter on it for a while. There's an outline of the sticker on the filter housing but it was paper when I bought it.

Anyway, it's a cheap try and the MAF probably needs cleaning anyway. I disconnected the battery to reset the system just to know quickly if it worked. It's been fine for about a tank and a half of fuel. The PO174 was the only code at the time, no others.

Anybody ever wonder why MAF isn't MAFS?

 

When you say "hosed it down"....?

 

It's a small red hose. Just being creative with my words.

 

AKA...clean the crap out of it .

 

Someone may really hose it down with water.
I never forget one guy used inch pounds on plugs instead of foot pounds . Needless to say it had blowby .
Plugs what kind are you using ,newest are sp546 mc ,I would use those or champions and carefully do plugs correctly with clean hands . These last 60k -so do them all new and replace boots ,clean cop contacts . These plugs are not easy to do and torque them in 25 to 28 foot pounds after you clean snout area out with carb cleaner.