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So a few min. in a drive thru In-n-out burger in notice the idle seems to drop. like when on the highway in 8th gear to save fuel? Is this normal? I had it in D w/ foot on brake then I put into park after that idle drop the car sort of lurched forward then when I went back into gear it made a not very nice sounding clunk.
 

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The Bacon Hauler (‘12 Cop Charger)
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Something that had been engaged, running, or otherwise energized (by current from the alternator) switched off stopped running, thereby reducing the load on the charging system, and the PCM responded accordingly - by reducing the RPMs and by extension the amount of current required from the alternator.

If you did not have the a/c on, the ambient temps must have been mild. Maybe they were mild enough that the (electrical) radiator fan cooled the engine coolant down to a temp that I longer required the fan to continue running.

So the PCM turned it off, and the increase in RPMs required to keep it running was rolled back, causing a noticeable drop in RPMs.

That's my best guess without more details or a vid clip to go off of.
 

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I have been having this problem since i purchased the car, 16 392 SRT. With everything off there are times when the idle drops below 500 rpm and the motor jumps around. Been to the dealer twice they said its a characteristic of the car. Called SRT they had me drop it off at the dealer and did diagnostic work and they said the same thing. I agree it happens during certain weather conditions but it does happen. I even got it to happen with the tech in the car. But if you never turn off the auto air it will never happen. If there was away to increase the idle speed of the car by a couple of hundred rpm's this might cure it but was told this is not possible, there is no adjustment for this. So the cure is never shut off the auto air. This seems to be related to the 392 and not the 6.2 or 5.7.....
 

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The Bacon Hauler (‘12 Cop Charger)
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I have been having this problem since i purchased the car, 16 392 SRT. With everything off there are times when the idle drops below 500 rpm and the motor jumps around. Been to the dealer twice they said its a characteristic of the car. Called SRT they had me drop it off at the dealer and did diagnostic work and they said the same thing. I agree it happens during certain weather conditions but it does happen. I even got it to happen with the tech in the car. But if you never turn off the auto air it will never happen. If there was away to increase the idle speed of the car by a couple of hundred rpm's this might cure it but was told this is not possible, there is no adjustment for this. So the cure is never shut off the auto air. This seems to be related to the 392 and not the 6.2 or 5.7.....
Pre-2015 LXs allow modification of the various states of idle speed (idle, ac on; idle, ac off, etc) with one of the aftermarket tuners, but i don't know if the 2015+ models allow it allow it as well.

I know the 2015s require a PCM swap to run a tuner, but i would be surprised if the functionality were no longer there with the new PCM. Now, that's a heck of an undertaking and investment of money all for the ability to change idle speeds, but if the behavior truly cannot be tolerated, the tuner+PCM mod would be the best (only?) solution I suppose.
 

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Pre-2015 LXs allow modification of the various states of idle speed (idle, ac on; idle, ac off, etc) with one of the aftermarket tuners, but i don't know if the 2015+ models allow it allow it as well.

I know the 2015s require a PCM swap to run a tuner, but i would be surprised if the functionality were no longer there with the new PCM. Now, that's a heck of an undertaking and investment of money all for the ability to change idle speeds, but if the behavior truly cannot be tolerated, the tuner+PCM mod would be the best (only?) solution I suppose.
HP Tuners lets you at that stuff. I don't think the Trinity does. I don't have access to an I2.
 

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Something that hasn't been mentioned is maybe the fan kicked on to cool your engine while you were going through the drive through??
 
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