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, I replaced the #8 spark plug and ignition coil and drove it for about 20 minutes, then P0174 code 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.

kh

 

i am reading that to mean that you still have p0308. Did You replace plug and coil with motor craft parts and/or did you save original plug/coil?

i would swap #8 plug with #1 and #8 coil with #5. then clear codes and drive/test. If you still have #8 misfire, then I would clear codes, swap #8 injector with #1, drive/test.

 

Yup it was the injector, did the switcharoo and the codes changed. Put a new injector in and good to go.

 

Awesome...nice call Later.

 

👍 👍

 

👍. Glad you are running again.

just curious, was the bad injector OEM?, and how did the O-Rings look?

if it is oem, and if you felt like taking the time, there are a lot of video on YouTube for bench cleaning these. ( involves running cleaner through in reverse direction). hurts to have a spare in the glove box. a plug, boot/spring/coil, injector can get you out of most situations

 

All OEM parts and O-rings looked good. Must have gotten some debris and clogged up the port