av8roc

2005 FX4 SCAB
5.4l 75k miles

Hey guys,

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.

No codes.

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!

DWNSTHJKN

Motorcraft SP507 or SP515. I too, use Champions, but only in my Toro.

av8roc

Thanks but that doesn't explain a rough running engine when cold. Are they prone to pre-mature failure? Maybe so but that is a different story.

Blue Blood

Did you disconnect the battery, discharge, reconnect, and then perform a re-learn on the idle?

av8roc

Battery and PCM were disconnected for hours while I did the repairs. How do you perform a "re-learn" on the idle?

99shortbed

Does it use coolant. If so may be headgasket leaking into cylinder and building up when the motor is off and fouls the plug when first starting up. When it warms up it gets all the water out and dries the plug therefore no foul and no miss. Or if your truck has an idle air control valve it could be bad

av8roc

No idle air control valve on the '05 and no, thankfully it doesn't lose any coolant.

I've been playing around with different tunes and it seems like the more aggressive the tune the more pronounced the issue is. I'm wondering if it had something to do with timing advance when engine is cold?

av8roc

Bumping this up. Anyone have other ideas?

99shortbed

I don't know man. Maybe try putting it back on the stock tune and seeing if that helps

av8roc

Tried that, same thing.