Hello everyone,

I'm new to the F150 world, and I need some help. I have searched around the forum and I can't find a thread with the problem I'm having.
I own a 2006 F150 FX4 5.4L 3v with 148,000 miles


I have a slight misfire, which I just assumed meant the truck needed a tune up

Here's what I've got going on right now

Slight Rough idle @ about 500 rpm's

You can feel Misfire in overdrive @1200 rpm's, not enough to throw a cade all the time. it is fine beyond 1800 rpm's

Active Codes:
P0300 Random Multiple misfire occurring sometime under load or going uphill



Changed the Following:
8 New spark plugs
8 new coil packs
8 new fuel injectors
MAF sensor
Variable Cam Phasers, timing chain guides and sensors.
Performance Oil Pump (since it was already opened up)
VCT Solenoids


When you put a reader on it does show slight misfires on #7 and #4 but not enough to throw a code.


Tried swapping COPs, Plugs and Injectors around but problem stays on those two Cylinders.


Vacuum pressure is strong and steady @20


Not Sure What to check next.




Any assistance would be greatly appreciated!

 

Brands? Also check your cats and try swapping injectors instead of just plugs and COPs

 

2 New Cats installed as well. All parts are Motor craft.

 

Test compression, fuel pressure, swap injectors

 

Have you checked your air filter housing seal? Just check it.

 

I have installed an S&B CAI. I have swapped injectors and compression test were great and steady

 

Did you check plug gap?

 

Have you checked the plug/wiring harness to those COPs and injectors. If the code stays with those cylinders and you have swapped everything around my next step would be to check the plug and harness. Good luck, let us know.

Tom

 

Is the engine tuned for the CAI? Try returning the intake to stock if it's not.

 

Also look at the FPDM located above your spare tire...