Jack Hodges

So, I have been through the whole cam phaser ordeal and found broken chain guides but I cannot get rid of a couple of nagging issues. My truck runs fine when its warmed up and I have no CEL or codes. It has a rough idle all of the time. When the engine is cold I have to feather the throttle when accelerating or it falls on it's face. It also backfires on acceleration when the engine is cold and falling on it's face. As soon as it is warm it runs fine other than the rough idle. STUMPED!
Here's what I have replaced over the last couple of years to try to get this engine running right:

• The entire timing set, guides and cam phasers. All OEM parts
• The crankshaft positioning sensor wheel/cog (during timing chains and guides)
• cam sensors
• COPs
• spark plugs
• catalytic converters
• downstream O2 sensors
• fuel injectors (installed Bosch 4 port upgrades[rebuilt])
• Had the Ford dealer check the computer for updates and he said there were none available or mine was completely up to date

I am out of ideas and really would appreciate some fresh ideas here!

Martian

Moved to 2004-2008

techrep

iTrader: (1)

Back firing would lead me to think Timing...

Jack Hodges

Can you even adjust the timing on stock engines and computers? I don't even know how to begin to check that. The dealer mechanic didn't mention anything about timing and said it was running as well as could be expected..... Take it to another dealer????

techrep

iTrader: (1)

Well... you just had all the timing apart...maybe something not put back correctly

Martian

^^^ this... without the tensioners on there tightly, the chains slip the cam sprockets really easily

Jack Hodges

I am absolutely certain that everything inside of the engine front cover is correct. I even took the front cover back off again to check all of the assembly over again thinking the same. It's nothing to do with the timing chain, guides, tensioners, torques or assembly.

I'm wondering about upstream 02 sensors?? Would this cause a stumble when cold? If so would that cause the continuous rough idle?

techrep

iTrader: (1)

maybe but, not backfiring

SCORGE

vacuum leak maybe? (not sure if that causes backfire)

Jack Hodges

Oh yeah, New OEM throttle body with positioning sensor. Removed and cleaned the MAF sensor but it looked perfect when it was removed, not dirty at all (and no I didn't touch the sensor). Truck accelerates perfectly when at operating temperature but still has rough idle. Never stalls though. Only stumbles and or backfires when cold (below operating temp) when accelerating from a dead stop. Runs too good at operating temp to be a timing issue (I think). I have read about a intake manifold leak problem but thought it had related fluid leaks that I do not have. Valve lash Problem???? Backfire is related to excessive fuel that can't be burned at the moment of the stumble? I worry about raw fuel in my new cats.....