Misfire at idle.

[stascom]

After the first very cold night, the car started ok. I let it idle for a minute and went to take off. The moment I slipped the clutch, it stalled. Odd. Wouldn't start again. Kept turning over without firing. When I exited the car, it honked (like it does when the engine is running). I thought it's just a typical, half-baked Ford ECM software not handling an engine stall correctly. It's probably still "thinking" the engine is running. Maybe why it wouldn't start. So I've disconnected the battery and left alone for 2hrs.
Came back and reconnected. It still wouldn't start but I heard a couple of ignition events. Battery was dying. I put a jump pack on. Another 5-6sec attempt to start - a couple of ignitions toward the end. 3 more times and it fire up.
Idled very rough (like misfiring). I blipped throttle a little, and it started to idle ok. Went around the block and it felt ok once on the road but at low RPM, turning circles, it didn't feel smooth. Pull back in, cycle through AP monitors, find "misfire." 39/39. Not knowing, if this is data for the current run cycle or historic, I stopped the engine and restarted. "Misfire" 0/0. Ok, so that's for the run cycle. Wait a bit and the idle sputters, drops low, I watch the Misfire count rack up to 38, and the idle stabilizes again.

No codes.

2017, 43k miles. Stratified tune for the past 3 or 4 years - no issues. What should I be looking at?

 

[sonicmn]

Just a silly theory, but stranger things have happened because of a dying battery that is struggling to take a charge in the cold... is the battery original? Cause 2017 is now 7 years ago and that could be part of it?

 

[stascom]

Maybe. 20F warmer today. No issues with starting or idling. Haven't watched the Misfire counter before. I get about 3 of them in a 10min drive.

 

[TyphoonFiST]

What is the condition of the battery? These cars run on a CanBus network. The voltage needs to be at least 12.5v or parts of the system start to become affected by low voltage. Were there any codes set?

 

[stascom]

No codes. Stayed warm and the car still runs fine. Been procrastinating on the battery.

 

[TyphoonFiST]

Could be the LPFS/Low Pressure Fuel Sensor on its way out the door. I did a DIY thread on its replacement.

 

[TyphoonFiST]

These cars do misfire * No car out there never misfires. It all depends the manufactory the threshold that needs to be met for the MIL/ Check engine light to go off.