2005 FX4 SCAB
5.4l 75k miles
In the process of fixing a dead spot/misfire condition I have recently replaced:
8 new plugs (Champion double plat)
8 new COP's (Accel super coils)
8 new injectors (Motorcraft)
That fixed the misfire and dead spot issue but now when the truck is cold I get a very rough idle and what feels like a misfire.
After about 5 minutes the truck runs beautifully. My MPG's have gone up from 11 to 15!
In addition to the above in the last couple of months I have also:
Removed and cleaned the MAF
Removed and cleaned the Throttle body
Replaced the fuel filter (motorcraft)
Replaced the FPDM (Dorman)
Installed two new VCT solenoids (Dorman)
Fixed IWE vacuum leak (new actuator)
Purchased and installed SCT custom tune for the truck. (Truck has CAI and Borla exhaust).
I'm scratching my head on this one. What would cause the truck to run rough when it's cold but run great once it has warmed up?
Is it possible I did damage to the CATs? I was getting a flashing CEL at times before I fixed the misfire and I've heard all that unburned fuel can damage them.
Any help is sincerely appreciated. Thanks guys!