Disabled Auto Start/Stop, engine stumbles at stoplights

[evan9r]

So I noticed after disabling Auto Start/Stop with FORscan that the engine stumbles at stoplights for the first 10 minutes or so.. I dont recall it being this bad before disabling the Auto Start/Stop but then again I rarely manually turned it off. At first I noticed switching to Sport mode or turning the A/C off makes the stumbling stop. Only once have I had it stumble with Sport mode. Has anyone else experienced this? I did replace the plugs and that made no difference. Truck is a 17' with 24,000

 

[Booth9999]

Sounds like you not running premium? Mine does this if I run regular.

 

[evan9r]

Nope, Ive always run premium. Ive thought it might be water or lower octane but changing the drive mode makes me think otherwise.

 

[HotLap]

So I noticed after disabling Auto Start/Stop with FORscan that the engine stumbles at stoplights for the first 10 minutes or so.. I dont recall it being this bad before disabling the Auto Start/Stop but then again I rarely manually turned it off. At first I noticed switching to Sport mode or turning the A/C off makes the stumbling stop. Only once have I had it stumble with Sport mode. Has anyone else experienced this? I did replace the plugs and that made no difference. Truck is a 17' with 24,000

Evan9r, good to get confirmation that you can indeed disable the auto stop/start function using FORScan. I hope you get this worked out, please let us know what you end up doing, thanks!

 

[Tlh235]

I'm glad I had MPT add this to my newest tune version....i hated when i would get in and forget to push that damn button.

 

[Magzx12r]

I get the same stumble when I stop. Just started with the hot weather and AC running hard.

 

[WhiteWidow18]

I also get a rough idle at stop more often than not. Dealership blamed it on the cooling fans being faulty. Got them changed under warranty last week and the issue is still prevalent.

 

[COMBS19]

Had a stubble idle now and again but after switch to Motorcraft SP542 spark plugs it has never happened again.

 

[evan9r]

I have replaced the plugs with 542s also. No change.

It has something to do with A/C and the PCM.

https://www.f150forum.com/f118/ac-compressor-cycling-off-385618/

 

[evan9r]

With cooler weather the problem is not as noticeable.

I did notice however its mostly from start up to operating temperature at stop lights with the AC on that it stumbles the most. Add a little throttle..enough to raise the RPMs a 100 or so.. and it goes away.

Could it be that the idle is set too low at cold temperature with the AC on?