Do 3.5s idle smoothly?

[Mosey]

Hi all,

Ever since I picked up my new-to-me 2021 PB, the engine has never idled “smoothly”, not like it is missing, just not smooth. It kind of reminds me of a Harley’s 96 CI A-motor, the one without a balance shaft. It runs very smooth at speed, just not at idle.

Is this your experience?

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[MisCalql8ted]

same, my 2021 pb also has a pretty rough idle it is worse when it goes from electric to idle, sounds almost unstable. took it in they said normal... lol

 

[RedTXV]

Non-powerboost here, but neither my '21 or '16 3.5 had a very smooth idle.

 

[oncechance]

My 2022 and 2014 eco's 3.5 idle smoothly.

 

[Antimatter22]

My '22 PB doesn't idle smoothly. Not sure if it always does it or not, but it does it often when I am paying attention

 

[Jglew82]

'22 PB here, also "choppy" idle. It doesn't really bother me, but it is noticeable as well.

 

[Oxford_Powerboost]

In fairness to the Powerboost - keep in mind that the engine isn’t actually idling in the traditional sense.

If the engine is running at a stop its either in cold start warm up or it’s charging the battery

In the warm up cycle, the PCM intentionally runs it a bit poor to dump extra fuel into the exhaust, heating up the catalytic converter faster.

When charging, understand that this engine is under a heavy load - probably a load similar to cruising at highway speeds. Therefore, you’ll feel some engine vibration as there’s a serious pull on the engine and it’s using a bunch of fuel and air to stay running. If you expect it to idle like an engine with no load on it, you’ll probably be disappointed, but once you realize how much work it’s doing, it makes more sense. Try eco idle on or off and see if you like it more. Eco idle puts a heavier load on the engine but it revs higher, so sometimes that’s a bit smoother

 

[Snakebitten]

Excellent post ^^^

I've had 3 trucks with the 3.5 Ecoboost and a couple of more in the family fleet. "idling smoothly" can be a subjective opinion, but on a Powerboost it would probably be rare to hear someone brag about smooooth idling.

If you were to monitor the PID for the high voltage battery's SOC, you would be able to see why it occasionally idles relatively smoothly, and then idles lumpy the rest of the time. As the previous post explained, that lumpy-vibrating idle correlates identically to a very rapid charging of the HV battery.

 

[Porpoise Hork]

Low speed idle when not charging is smooth, but when it tries to charge the battery it will lug a little but until it ramps the rpm up to about 1500 +/- then smooths out. Kind of makes sense it would lug at low rpm when charging due to the extra load so I wasn't very concerned about it.

 

[Mosey]

I think oxford_pb has it correct. I can tell when my system is charging as the engine will rev up to around 1300 rpm’s. I am thinking that the roughness I feel probably begins when the system calls for charging and begins to ramp up the idle.

The PB is just a different beast.

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