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Hello Everyone!

I'm hoping that someone here may have some insight on the following situation. I will be going to the dealer on Monday but thought I'd try to get some input here as well. Truck has a 32, 000 miles and no CEL light.

When I have the AC on max and the AC fan fan on high, the truck shakes when coming to a stop. I blame this due to the fact that rpms drop to about 490 causing the truck to shake. Once the truck detects the drop in rpms (I assume this is what happens), the rpms pick back up to about 550 or so, and the idle smooths out. It seems to be worse when it is hot outside. Now that temps have cooled a bit, it is not as noticeable. As I increase fan speed when having the AC on, the shake becomes more and more noticeable when stopping. The AC compressor clutch engages just fine, AC blows nice and cold air. One day, when coming to a stop, the truck shook so bad, my stability control light started flashing, and then turned off when the idle smoothed out. Other than this, all is great. I have no idea if a sensor somewhere could be affected by the summer heat and not reading right? I can't see too much amperage being pulled by ac fan or compressor, or radiator fan as that means fuses should be going out. But I could be wrong.vAs I mentioned above, all is good until I turn the AC on and put the fan speed on higher speeds. Lower fan speeds and AC on do not cause the truck to shake. Worse in hot days, barely noticeable when cool outside. Maybe the idle is not set right on the truck? Idle set too low perhaps? MAP sensors? Throttle body? Any input will be highly appreciated!!! Thanks!!!
 

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It is normal across ecoboost and is believing to be low rpms as you said. Deal with it or raise rpm idle in tune.
Thank you for your reply! I've read in several forums where people stated this being normal as well. At the same time, I've read that it is not normal. I've read where these engines should idle at the same rpms regardless of load. I figured that if the shaking was bad enough to catch my attention, it would catch everyone else's attention who drives an ecoboost. Dealership said they haven't heard anyone complain about this issue. I have several friends who own similar trucks (2015 - 2019 models) and none report the symptoms my truck is having. As I mentioned in my original post, the truck shook so bad one time, that the stability control light started flashing and that's because the truck almost stalled due to rpms dropping. It was 100 degrees + that day. I pump the same gas that everyone in town pumps (including my friends) so I had ruled out bad fuel. The dealer service manager said he will check the spec rpms and see if all is good in my truck. I guess I can ask him to bump up the stock idle. AC compressor runs smooth and AC blows ice cold. No on/off compressor cycling. I have included two pictures showing what rpms look like when coming to a stop. First one is with with AC on and fan speed on high (that's how much rpms drop), and second one is with AC on and fan speed on medium to low (rpms never dip below that level). I appreciate if you, or anyone else, can give me any input on what my rpms look like. Thanks!!!
 

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30,000 on my 18.
Texas heat.
It might be considered normal for the occasional shudder at low rpm, which I have experienced myself. But very rare. So rare I wouldn't let anyone mess with it.

I don't think it's normal for it to be consistently shuddering.

I don't know why my truck dropped in rpms below normal on those occasions

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Discussion Starter #5
30,000 on my 18.
Texas heat.
It might be considered normal for the occasional shudder at low rpm, which I have experienced myself. But very rare. So rare I wouldn't let anyone mess with it.

I don't think it's normal for it to be consistently shuddering.

I don't know why my truck dropped in rpms below normal on those occasions

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Thank you for replying! I appreciate it! I agree with you. If it was something my truck was doing rarely, I would not worry about it. However, it does it every time I come to a stop with AC on and fan speed on high. The shaking is worse when temperatures were close to 100. Now that it has cooled down to the mid 80's in Central GA, the rpms don't dip as much when stopping and the shaking is barley there. My AC compressor seems to engage fine and the AC blows nice and cold. I've changed air filter and in cabin filter at 30,000 miles. When I turn the truck first thing in the morning or after being parked all day at work, the rpms naturally stay up a bit until the engine warms up. During this warm up period, the rpms won't dip. It is after the engine has reached operating temp based on the engine temp gauge. I had to tow a friend of mine last night (16ft trailer with a single cab nissan frontier on it) for about thirty miles and the truck performed flawless. As matter of fact, my mpgs never changed from 17.1. Great! I am at a loss at this moment. I'm just trying to be proactive. As WooBoost suggested above, I wonder if it is a stock idle issue. Does your truck happen to idle at similar rpms as mine per the pictures above? Thanks!!
 

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My 18 does the same thing your describing .
28k miles


-Brian

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Discussion Starter #7
My 18 does the same thing your describing .
28k miles


-Brian

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Hi Brian! Thank you for replying! I’m sorry to hear your truck is experiencing the same symptoms as mine. Have you looked into it or talked to anyone about it? Any info?
Thanks!
 

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I'll take a pic of tachometer at red-light next time I'm in the truck.

Don't want to report inaccurately. Especially when a 100rpms could make all the difference in the world in this scenario

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I'll take a pic of tachometer at red-light next time I'm in the truck.

Don't want to report inaccurately. Especially when a 100rpms could make all the difference in the world in this scenario

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Thank you sir! I appreciate this very much! I usually turn my AC on on hot days by turning the AC knob counterclockwise to turn on MAX AC and fan on high. This is when my symptoms are the worst when coming to a stop. Looking forward to hearing back from you and compare tachs.
 

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Hi Brian! Thank you for replying! I’m sorry to hear your truck is experiencing the same symptoms as mine. Have you looked into it or talked to anyone about it? Any info?
Thanks!
Honestly I’m not very worried about it . I did notice it a couple times And thought it was odd .
I think it’s related to the load on the AC
I also run premium (93) gas


-Brian

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Hello Everyone!

I'm hoping that someone here may have some insight on the following situation. I will be going to the dealer on Monday but thought I'd try to get some input here as well. Truck has a 32, 000 miles and no CEL light.

When I have the AC on max and the AC fan fan on high, the truck shakes when coming to a stop. I blame this due to the fact that rpms drop to about 490 causing the truck to shake. Once the truck detects the drop in rpms (I assume this is what happens), the rpms pick back up to about 550 or so, and the idle smooths out. It seems to be worse when it is hot outside. Now that temps have cooled a bit, it is not as noticeable. As I increase fan speed when having the AC on, the shake becomes more and more noticeable when stopping. The AC compressor clutch engages just fine, AC blows nice and cold air. One day, when coming to a stop, the truck shook so bad, my stability control light started flashing, and then turned off when the idle smoothed out. Other than this, all is great. I have no idea if a sensor somewhere could be affected by the summer heat and not reading right? I can't see too much amperage being pulled by ac fan or compressor, or radiator fan as that means fuses should be going out. But I could be wrong.vAs I mentioned above, all is good until I turn the AC on and put the fan speed on higher speeds. Lower fan speeds and AC on do not cause the truck to shake. Worse in hot days, barely noticeable when cool outside. Maybe the idle is not set right on the truck? Idle set too low perhaps? MAP sensors? Throttle body? Any input will be highly appreciated!!! Thanks!!!
I have 28K on my 18 and have had slight shudders at idle. I chalked it up to the low RPMS as many others have, but have never had it shake so bad that my stability control light illuminated. I will say that this is the worst transmission i have ever driven though =)
 

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I have 28K on my 18 and have had slight shudders at idle. I chalked it up to the low RPMS as many others have, but have never had it shake so bad that my stability control light illuminated. I will say that this is the worst transmission i have ever driven though =)
This 10 speed has amazing potential.
But you aren't likely to experience how well it can perform without tuning it.

If I had to decide between the transmission tune VS the engine tune, I'd actually take the transmission tune.

The oem motor is already the most powerful HP-per-lb truck in the class. But putting that power to the ground is a bit clumsy if the transmission strategy isn't dialed in.

I've got quite a few different tunes and they all bring something to the table, but Matt at GearHead nailed my transmission. Truly made me love my truck more.

(sorry about the hijack)

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This 10 speed has amazing potential.
But you aren't likely to experience how well it can perform without tuning it.

If I had to decide between the transmission tune VS the engine tune, I'd actually take the transmission tune.

The oem motor is already the most powerful HP-per-lb truck in the class. But putting that power to the ground is a bit clumsy if the transmission strategy isn't dialed in.

I've got quite a few different tunes and they all bring something to the table, but Matt at GearHead nailed my transmission. Truly made me love my truck more.

(sorry about the hijack)

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I actually just started a thread and mentioned a transmission tune. So this is possible to fix with a programmer? Do they adjust shift points? Im very interested in this.
 

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Thank you all for replying. Snakebitten, no worries. I am happy to hear that you are enjoying your truck! As Smarko was saying, sometimes I desire more out of the 10R80 transmissions these trucks come equipped with. I have noticed that, when babying the truck, the transmission can shift fairly hard at times (particularly low gears). But, when giving it constant acceleration, it shifts pretty darn smoothly. In my opinion, I think my truck drove better towing 5,000 lbs than when not towing, lol. So far I am very impressed with the vehicle and enjoy driving it. All is great but the idle. Smarko, I agree. I'm not sure why the truck shook so bad that one time. Kind of odd. I had my plugs changed the day before (gapped at 0.030) and drove fine after I left the dealership. That happened the day after and hasn't done it again. It was very hot that day (over 100 degrees here in Central GA).

So, I think I may have narrowed the rough idle to one thing and will have the truck checked out on Monday. It has to be the 1234yf AC compressor charge. The reason why the truck runs fine with AC full blast in the morning time or night time, is because the temperatures outside are cool Since temps are cool, pressure doesn't build up in the compressor to cause resistance on the pulley when the clutch engages. Therefore, the AC compressor doesn't pull the rpms down on the engine. When it is hot outside, the pressure in the AC compressor builds up causing resistance on the pulley when the clutch engages which in turn, pulls the rpms down. Pressure must be building up a bit, perhaps due to overcharging (wrong poundage) in the AC compressor. However, not high enough to trigger the high pressure switch to shut compressor off but high enough to put strain on the serpentine belt. I could be wrong though. Also, the reason why I think this is the issue, is because the truck idles fine when it is hot outside only if I have my fan speed on medium to low. When to this, there is less air volume flowing through the cooling coils thus demanding less cooling power thus keeping refrigerant pressure down. What do you all think? Like I said, I'm having the truck checked out Monday. I know it can't be normal load causing this as everyone with the same truck would be experiencing this. Besides, I would imagine that fuses would be going out if that latter was the case. Please let me know if you all think I'm crazy for thinking this! lol
 

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This might be a case where a reset on the computer might help bring your truck out of the extreme and more in line with others' results. Battery disconnected, headlights on for 10 mins or so. Let it relearn.

It's a cheap, low labor, low-risk item. I would give it a try, knowing that when I swapped out spark plugs the first time, my truck ran like **** til I reset it. Then again, mine were about .015 gapped too far.

Computers are weird. Pretty much gotta chase down and eliminate variables here.
 

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I actually just started a thread and mentioned a transmission tune. So this is possible to fix with a programmer? Do they adjust shift points? Im very interested in this.
I've read that some of these tuners do. With good results even. I would read up on that. There's a few threads where it's mentioned in the performance section I believe.
 

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This might be a case where a reset on the computer might help bring your truck out of the extreme and more in line with others' results. Battery disconnected, headlights on for 10 mins or so. Let it relearn.

It's a cheap, low labor, low-risk item. I would give it a try, knowing that when I swapped out spark plugs the first time, my truck ran like **** til I reset it. Then again, mine were about .015 gapped too far.

Computers are weird. Pretty much gotta chase down and eliminate variables here.
Dealership got the KAM reset on the truck when I got my plugs changed. Ford manual states plug gap should be between 0.75mm and 0.85mm (0.030 and 0.033). I got mine gapped at 0.030. A while back, I tried doing what you suggest. However, I am not familiar with how these new battery cables work on the battery terminals. I tried disconnecting the negative terminal by loosening up the nut but could not get it off the battery post. I got it loose but would not slide up after I tried pulling so I just let it be. I know this should be easy as I've changed many batteries throughout the years but this one got the best of me. Maybe I wasn't pulling hard enough because I didn't want to tear something up in my new truck. lol. Any suggestions on how to remove the battery cable from the battery post? Thanks!
 

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Good suggestion on the computer reset and re-learn procedure. Costs nothing!

Also, you mentioned you had plugs changed the day before?

Man, that's a BIG flag!
These trucks are NOTORIOUS for plug sensitivity. So many fellas swear they were careful and that their new plugs, wires, clips looked perfect and they were careful putting them in. Only to discover a plug or wire was indeed the culprit on re-examination.

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Discussion Starter #19
Good suggestion on the computer reset and re-learn procedure. Costs nothing!

Also, you mentioned you had plugs changed the day before?

Man, that's a BIG flag!
These trucks are NOTORIOUS for plug sensitivity. So many fellas swear they were careful and that their new plugs, wires, clips looked perfect and they were careful putting them in. Only to discover a plug or wire was indeed the culprit on re-examination.

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Plugs were changed at the dealership. The symptoms before the spark plug change are still the same after the spark plug change. No difference. If it was a plug, coil, injector, or wire harness issue, I would assume the symptoms would be present regardless of AC on or off. I towed my buddy's truck two nights ago and it was a dream towing with my truck. I suspect if the issue was engine/fuel related, towing 5000lbs should have exacerbated the symptoms. I agree, this is why I went for plug change. I thought that could have fixed the idle but it didn't. The dealer did do the KAM reset and that did not help. I guess I'll figure out how to remove the negative end of the battery terminal to do the reset myself before going to the dealership on Monday.
 

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Plugs were changed at the dealership. The symptoms before the spark plug change are still the same after the spark plug change. No difference. If it was a plug, coil, injector, or wire harness issue, I would assume the symptoms would be present regardless of AC on or off. I towed my buddy's truck two nights ago and it was a dream towing with my truck. I suspect if the issue was engine/fuel related, towing 5000lbs should have exacerbated the symptoms. I agree, this is why I went for plug change. I thought that could have fixed the idle but it didn't. The dealer did do the KAM reset and that did not help. I guess I'll figure out how to remove the negative end of the battery terminal to do the reset myself before going to the dealership on Monday.
With that stuck on, i'd also be cleaning up terminals. Not good ground etc could give your computer fits too. Seems a little knit-picky, but I always go after the little things first before spending money. Especially if I stumbled on something like a stuck battery terminal like you luckily did. Those stupid little variables are responsible for their share.
 
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