2006 5.4 Lariat Cylinder 5 and 6 misfire and passenger bank running lean
 

Hello,
I literally just joined this forum in the past hour. I am a Senior at NCSU and just purchased my first truck on my own this past December. Its a 2006 F150 Lariat with a 5.4l and 84k miles.
A few weeks back it start running very rough when I would punch the gas hard and it would also sound like it was backfiring or popping through the exhaust when I would first start it up and hit the gas but went away once the truck warmed up. The tach would jump high and the truck would stumble very badly and then clear up after a few seconds. Eventually the check engine light would start flashing while doing this but would go away once I let up on the gas pedal and the truck returned back to a normal driving speed/rpm. Then the check engine light would came on and remain on. I had it checked and it was Cylinder 6 misfire so I replaced both the plug and coil (by the way, what in the Hell was Ford thinking with these spark plug designs??!!) and the problem went away and everything cleared up. Then the popping in the exhaust returned a few days later and then came back the stumbling. Only this time it would mostly happen when the truck was on a pull going up a hill. Then a few days ago I came home for spring break with the intentions of doing a tune up and replacing all of the plugs and coils. Had the code ran and this time it was cylinder 5 and 6 misfiring. I replaced all of the plugs and coils and the problem still exists cylinders 5 and 6 are still misfiring and for some reason one of the banks is running lean (cant remember off the top of my head which one).
Going up a hill the truck shakes really bad and honestly feels like the transmission is about to take a crap but I know it is the motor because when the shaking starts and it starts running really rough the check engine light starts flashing again but goes away after I ease off the throttle.
If anyone out there could give me an idea as to what in the Hell is going on with my truck id really appreciate it. Ive looked through some past threads and I have found a few things similar to my issue but I honestly dont have time to spend hours looking through everything since I only have a few days left of my break before I have to be back in Raleigh and at work.


Also, I bought the truck through a private sell. I know...probably not the smartest decision I ever made...
Thanks again,

-Michael
NCSU
Senior Human Biology, Nutrition Science
Firefighter/EMT
Safety Technician for NCSU Fire Protection
Undergraduate Teaching Assistant

do you have acces to a scan guage? this way you'll be able to watch short term fuel trims, i'am thinking your injectors need to be considered.

id take it easy on the gas pedal and major loads... that popping/backfiring is detonation which will lead to really bad things such as a thrown rod, or burned piston and valves.

the check enigne light on the dash was flashing? not the O/D light

Make sure all the coil connectors are connected and you didn't crack a plug. The CEL flashing means you are damaging the cat converter from all the misfiring. What plugs did you use? The lean code can be caused by the misfire because the oxygen in that cylinder is not getting burned and the O2 sensor is reading it. If you can't get it straightened out send me a PM and we can meet. I work in Smithfield and live 20min south of Raleigh.

I know this is an older thread but thought I would throw this in. Clean the Mass Airflow Sensor in the intake. You'll see two fine wires parallel to each other. Mine had a little crap built up on them and gave me the lean bank code. I wet a cutip with alcohol and gently cleaned them. Problem solved!