Very rough idle when the AC is on? (video in post)

[John94]

Hi Guys,

decided to give this forum a try as y'all seem really knowledgeable

My Bronco starting having a really rough idle today when the AC was turned on. Engine got louder, steering wheel had slight vibration and the actual engine compartment is vibrating as well. RPM's seemed to stay relatively normal, around 0.8k at idle.

I'm not a big car tech guy so any help is appreciated.

Is this normal? anyone else have this issue?

I tried to make a video showing the vibrations.. kinda hard, so I used a sticky note as a visual. When the video starts the bronco is idling normally, then I turn the AC on and you can see and hear a big difference !

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[SubmarineNuke]

800 seems high for an idle. Per my tach I’m usually about 5-600 when I’m at a stop light. And I run the AC religiously as I live in the devils armpit known as houston

 

[John94]

After some google "research" it appears it could be a number of things, but the main issue that I see cited is a dirty or faulty IAC valve - I believe that's an Idle Air Conditioning valve.. trouble is that I do not know where to locate that..

 

[drew707]

After some google "research" it appears it could be a number of things, but the main issue that I see cited is a dirty or faulty IAC valve - I believe that's an Idle Air Conditioning valve.. trouble is that I do not know where to locate that..

IAC stands for Idle Air Control and is an older technology. The modern systems of the Bronco don't utilize an IAC. Though I don't really have any further diagnosis for you from a virtual session.

 

[John94]

IAC stands for Idle Air Control and is an older technology. The modern systems of the Bronco don't utilize an IAC. Though I don't really have any further diagnosis for you from a virtual session.

good to know - it’s not much but it’s progress!

 

[Ford Motor Company]

Hi Guys,

decided to give this forum a try as y'all seem really knowledgeable

My Bronco starting having a really rough idle today when the AC was turned on. Engine got louder, steering wheel had slight vibration and the actual engine compartment is vibrating as well. RPM's seemed to stay relatively normal, around 0.8k at idle.

I'm not a big car tech guy so any help is appreciated.

Is this normal? anyone else have this issue?

I tried to make a video showing the vibrations.. kinda hard, so I used a sticky note as a visual. When the video starts the bronco is idling normally, then I turn the AC on and you can see and hear a big difference !

Hi there. Can you send us a DM with your VIN and dealership info? I can look into this for you.

 

[Hudman316]

Seems normal to me.

 

[EKOBX]

Hi Guys,

decided to give this forum a try as y'all seem really knowledgeable

My Bronco starting having a really rough idle today when the AC was turned on. Engine got louder, steering wheel had slight vibration and the actual engine compartment is vibrating as well. RPM's seemed to stay relatively normal, around 0.8k at idle.

I'm not a big car tech guy so any help is appreciated.

Is this normal? anyone else have this issue?

I tried to make a video showing the vibrations.. kinda hard, so I used a sticky note as a visual. When the video starts the bronco is idling normally, then I turn the AC on and you can see and hear a big difference !

I have the 2.7 and mine does the same thing on hot days. I’ve noticed there are some flaps in the front that open up and the cooling fan seems to be on overdrive. I’ve not tried it with or without AC go see if it changes. I’m assuming it is simply the cooling system ramping up to keep the engine temp down, but it is quite loud and rough

 

[flip]

Mine does the same. Was just looking at the WSM and these run a variable displacement compressor but the hi and low sides operate at lower psi than some of the R12 or R134A systems from the past. Based on others I've been in that do this, I'll say it's a normal characteristic. That's not dismissing the annoyance, just saying there's probably not much that can be done for it. If you would have an issue like a restriction or not enough air flow, it could make pressures go up, making the compressor work harder which could telegraph more shake than normal into the vehicle. You'd likely have other problems if this was the case.

 

[John94]

I have the 2.7 and mine does the same thing on hot days. I’ve noticed there are some flaps in the front that open up and the cooling fan seems to be on overdrive. I’ve not tried it with or without AC go see if it changes. I’m assuming it is simply the cooling system ramping up to keep the engine temp down, but it is quite loud and rough

I really appreciate the feedback! Having spent a pretty penny on the bronco and the car market being what it currently is, I get nervous when I feel anything suspect with the power train

 

[TABadlands]

Sounds like the condenser fan speeding up? I didn't really hear anything unusual from your video.

 

[cowman]

You have to have air flow across the air conditioner condenser to make a AC to work... sitting and idle has no air flow.... so the fan kicks in..... kind of like your house AC.... it's not moving so it has a fan that kicks in to cool the coils.... my Bronco does the same thing.....

 

[EKOBX]

I really appreciate the feedback! Having spent a pretty penny on the bronco and the car market being what it currently is, I get nervous when I feel anything suspect with the power train

Me too! I’ll let you know if anything changes. It seems like it happens when it’s above 80.

 

[A907Chick]

I posted about this exact thing today, I searched "vibration when AC is on" but your post didn't come up. Mine just started doing this yesterday. Our temps have been high the last few weeks. This week they are lower and this is the first time I noticed it. It's so rough that I can feel my seat and what feels like the whole undercarriage vibrating. I don't think it's normal.

 

[John94]

I posted about this exact thing today, I searched "vibration when AC is on" but your post didn't come up. Mine just started doing this yesterday. Our temps have been high the last few weeks. This week they are lower and this is the first time I noticed it. It's so rough that I can feel my seat and what feels like the whole undercarriage vibrating. I don't think it's normal.

Yeah, you’d think this thread would be getting more attention. I know I’m not a mechanic or engineer… but I’ve owned 7 different vehicles from all different brands and years and NONE of them did this in the summer (or ever).

if you do decide to take yours to the dealer, please let me know what they say

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