P0308 and P0174 codes on 2008 F150

[madcow]

Need some help from the ODT Gearheads.

I have a 2008 4.6L STX 4x4 model F150 (140k miles) that is idling with a little more vibration than normal at around 750 rpm, vibration increases as I gave it more gas and accelerate, also there is some hesitation during acceleration. If I rev it while parked, there is some backfiring at the exhaust.

It first threw a P0308 code (#8 cylinder misfire), I replaced the #8 spark plug and ignition coil and drove it for about 20 minutes, then P0174 code (lean bank 2) came up.

What I have done so far:
Replaced #8 Spark Plug and Coil
Cleaned the MAF sensor
Cleaned Throttle Body
Checked Air Filter
Checked for vacuum leaks
Added Seafoam at last fill up.

None of my fixes have cleared the codes or helped with the vibration issue, any help would be appreciated on where I need to look next.

 

[Gaffer1968]

Vibration....forget computer codes. How are the motor mounts on it?

 

[madcow]

Vibration....forget computer codes. How are the motor mounts on it?

Haven't checked it, but will look at it next. Rough idle started then CEL came on with P0308 code, so never expected to look at the motor mounts.

 

[madcow]

Motor mounts look good.

I figured out it was the injector, did the switch with other cylinders and threw a different fault code. Swapped it out, engine is now running smoothly with no vibration.

After eliminating spark, then air, fuel had to be next.