4.0 V6 Cold Starts and then stalls.

[BeefKeith]

My 2003 XLT w/ the 4.0 starts good in the cold, but will start to slowly stall and is unresponsive to me tapping the gas. If it doesn't stall, it will just sputter around <500 RPM before eventually recovering. How can I fix this?

 

[Shran]

No need to post duplicate threads on this issue, one is enough

Does it eventually run OK once it's warmed up? Any codes/check engine light present? What about warm weather?

 

[BeefKeith]

No need to post duplicate threads on this issue, one is enough

Does it eventually run OK once it's warmed up? Any codes/check engine light present? What about warm weather?

Yeah sorry about that, new to TRS.

Once it warms up and gets moving it runs fine. Have had no issues with the engine's performance in warm weather or in the cold. Not throwing any codes, although I had a 5min window of flashing check engine about a month ago, but didn't have any show up on the scanner after that.

 

[Shran]

Flashing CEL usually indicates a misfire.

Any recent work done to it? When did you last do spark plugs, fuel filter, maintenance stuff?

No throttle response when cold leads me to suspect a fuel issue or lack thereof, could be low fuel pressure, ice/water in the fuel lines, plugged up filter, weak pump, bad fuel pressure regulator... or a bad coolant temp sensor. If it's reading warm when the engine is cold, it'll run really lean when you open the throttle.

You could have someone who has a decent scan tool drive it and watch the live data to see if something is out of whack. Or you could throw some parts at it, I would start with plugs, fuel filter, air filter, a bottle or two of HEET, and a coolant temp sensor unless you have done those recently.

 

[BeefKeith]

Flashing CEL usually indicates a misfire.

Any recent work done to it? When did you last do spark plugs, fuel filter, maintenance stuff?

No throttle response when cold leads me to suspect a fuel issue or lack thereof, could be low fuel pressure, ice/water in the fuel lines, plugged up filter, weak pump, bad fuel pressure regulator... or a bad coolant temp sensor. If it's reading warm when the engine is cold, it'll run really lean when you open the throttle.

You could have someone who has a decent scan tool drive it and watch the live data to see if something is out of whack. Or you could throw some parts at it, I would start with plugs, fuel filter, air filter, a bottle or two of HEET, and a coolant temp sensor unless you have done those recently.

I put new upstream O2 sensors in it a month ago and it ran better, but that's also when the issues started. I have new spark plugs in there too, but I'm not sure that was an issue in the past.

I'd imagine the dealership the prior owner got it from last year put a new fuel filter in then, but I am not sure. Once it thaws out in the spring I was planning on doing a more intense overall than just the simple maintenance.