Forddude86

I have a 2000 with a 5.4 and when the outside temperature is low, it will sometimes idle very rough and chug like it wants to die. But, once I touch the throttle it clears up but does it again when it hits idle. Once the motor runs for awhile it will idle fine...ish. If the outside temperature is a bit higher, it won't do it at all. It will periodically throw the codes of bank 1 & 2 running lean. I've replaced the tps and iac valve but to no avail. Any ideas?

Forddude86

No one has any ideas?

techrep

iTrader: (1)

Bank 1 & 2 running lean means your motor is not getting enough fuel or too much air. When is the last time you changed your fuel filter..

sam29078

Vacuum leaks? Intakes gaskets bad?

Forddude86

Update: I've replaced tps, iat, iac, fuel filter, fuel pressure regulator, crank shaft position sensor, several vacuum lines, and cleaned the throttle body. After fuel pressure regulator, it quit throwing lean codes but it still chugs in cold weather before the motor is warm. Any other cheap(ish) parts I can load into the parts cannon?

Blckwlf

Vacuum or exhaust leak is my guess...

Forddude86

It has the rear 2 exhaust manifold bolts broken causing a leak. Could that really cause the cold weather chugging?

Martian

Put in a good fuel system / injector cleaner like Techron or Gumout With Regane. Avoid Lucas. I don't see why the exhaust leak would cause the engine to run lean since that's at the *** end of the combustion process... hopefully I can learn that today, if that's true. But a vacuum leak can definitely cause the lean codes.

Forddude86

I've gone through vacuum lines a couple times. Would a vacuum leak plug itself once it's warm? It only chugs when motor is cold and the outside temp is below 40.

Martian

Nope. An exhaust leak would / could, though. Any good exhaust shop with a smoke machine can test for leaks cheap.