ford 4.6L PO306 and many times also a PO420?

W

wayne p

New member
I have changed the coil pack, wires, plugs, checked the compression and it is the same on all cylinders (and within specs), I have checked the vacuum and it is steady, changed the fuel filter, changed the MAF, changed the air cleaner.

I am noticing a misfire 'shake' at all RPM ranges as I drive, but less so in park. I am noticing that it runs pretty good mostly, but often it will starting tripping up on itself. When this happens, the idle is very bad, the miss is very apparent.

My question: Fuel Injectors next? Bad wire? I changed the plugs twice since this started happening. Bad Crank Sensor/reluctor?
 
Start by cleaning out your IDLE AIR CONTROL VALVE and THROTTLE BODY. Examine your PCV valve and follow the rubber hose routings on your VECI map. Use Amsoil Foaming Cleaner and Gum-out to do this job. Power wash engine. If there are any weaknesses, they will show up here. Run the engine with the cleaners spraying right through the intake system. Use them in ALL vauum ports you can find. This will clean the O2 sensor(s) and remove carbon from the converter. On many Ford engines, you have to remove a throttle cover to gain access to the PCV. Also, check the vapor lines from the canister to the throttle body. Good luck!!
 
Excessive EGR gas recirculation flow to the misfiring cylinder or maybe a vacuum leak that's worse for the air flow to that cylinder. Make sure the PCV valve and system are flowing properly. Ford has special technical service notes and procedures to diagnose "lean misfires". Read the internet hits below.

http://www.google.com/search?sourceid=navclient&ie=UTF-8&rlz=1T4GGLL_enUS329US329&q=ford+lean+misfire+codes
 
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