Why does my idle speed dip a few times per minute after engine warms up?

[GJarrett]

My EcoBoost has always experienced a lowering of idle speed once every twenty seconds or so after the engine warms up... I have noticed that the idle speed does not seem to dip when the engine is cold.

I now have a 2.0 block with balance shaft delete and have noticed these idle speed dips have gotten a lot worse. A couple of times the rpms have dipped so low it killed the engine.

Why is it doing that and is there a fix?

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[Jstang23]

My EcoBoost has always experienced a lowering of idle speed once every twenty seconds or so after the engine warms up... I have noticed that the idle speed does not seem to dip when the engine is cold.

I now have a 2.0 block with balance shaft delete and have noticed these idle speed dips have gotten a lot worse. A couple of times the rpms have dipped so low it killed the engine.

Why is it doing that and is there a fix?

If your engine is tuned its most likely an issue with the tune. However, the dip in idle speeds is normal in most engines as that is the A/C compressor clutch engaging and disengaging. If it dropped so low it killed the engine then your tuner needs to raise the idle rpms a bit to all for the A/C compressor to do its thing. There is a slight chance that your compressor is going bad, as a burnt clutch would require more energy to turn the compressor, thus stalling your engine.

 

[Chacho71]

So this just happened for the first time on my way home from work today. No tune and completely stock. I also had a notification from my Ford pass app that my car has gone into deep sleep mode. It’s a daily driver and the deep sleep mode has happened about 5 times since new. Ford tech said they found no issue.

 

[Nagare]

So this just happened for the first time on my way home from work today. No tune and completely stock. I also had a notification from my Ford pass app that my car has gone into deep sleep mode. It’s a daily driver and the deep sleep mode has happened about 5 times since new. Ford tech said they found no issue.

Deep sleep mode (based on what just happened to me this week) is related to Sync system updates. Once you start the car again, it'll no longer be in deep sleep mode.

 

[Stangalang]

So this just happened for the first time on my way home from work today. No tune and completely stock. I also had a notification from my Ford pass app that my car has gone into deep sleep mode. It’s a daily driver and the deep sleep mode has happened about 5 times since new. Ford tech said they found no issue.

I will say, I received the deep sleep alert when the battery is low voltage. Generally I drive my Mustang 2-3 times a week even throughout the winter months. If I don't drive it for a week I get a deep sleep notification. I found out the battery was the original one from 2018. Replaced it a few weeks ago, and now no problems regarding that. I doubt it's related to the inital post, but I'd check your battery. Can't hurt.

 

[markayash]

I will say, I received the deep sleep alert when the battery is low voltage. Generally I drive my Mustang 2-3 times a week even throughout the winter months. If I don't drive it for a week I get a deep sleep notification. I found out the battery was the original one from 2018. Replaced it a few weeks ago, and now no problems regarding that. I doubt it's related to the inital post, but I'd check your battery. Can't hurt.

I noticed mine will drop for a couple seconds if I roll the back windows up so I watched the voltage and it drops. Ford said Battery and charging are good..
Only seems to do it when it's cold.

I bought mine used so not sure how old the battery is

 

[luca1290]

I noticed mine will drop for a couple seconds if I roll the back windows up so I watched the voltage and it drops.

Every car does this, the window motor draws a lot of current (check the amperage of the fuse!) which in turn makes the alternator a little harder to turn.

 

[markayash]

Every car does this, the window motor draws a lot of current (check the amperage of the fuse!) which in turn makes the alternator a little harder to turn.

Good to know, always bugged me something was wrong.

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