2016 mustang gt idle issue

[Romclean]

Does anyone know if this is normal? My 2016 mustang gt randomly drops 100-200rpms while in park. I did notice that the air/fuel ratio drops to 13.5 from the 13.9-14.2 range and that the vacuum jumps from 17.9 inhg to 20 than down to16.9-17.1 when it happens. No check engine light or performance lost.

2016 mustang gt
52k miles
93 octane gas only
Only mod is a roush catback with x pipe.

Sponsored

 

[Drewgamer]

I don't know a lot about the workings on these (or really any) automobile engines, but it sounds normal to me. My last car ('07 Mustang GT) and my current car do this as well (both manuals if that makes any difference).

 

[Elp_jc]

Hey OP, please elaborate more on your 'issue'. Does it go down just once? Is it fluctuating back and forth 200 rpm? We need more detailed info to comment. What I can tell you is my car does something similar on cold starts. It goes up, and loud, as expected. Then idle speed starts going down, and when it's around 800 rpm, then it starts fluctuating up and down a little, and then it settles around 650 rpm. If I turn A/C on, then it settles around 800 rpm. Unless it's incessantly fluctuating that much, it sounds 'normal' to me.

 

[Romclean]

Hey OP, please elaborate more on your 'issue'. Does it go down just once? Is it fluctuating back and forth 200 rpm? We need more detailed info to comment. What I can tell you is my car does something similar on cold starts. It goes up, and loud, as expected. Then idle speed starts going down, and when it's around 800 rpm, then it starts fluctuating up and down a little, and then it settles around 650 rpm. If I turn A/C on, then it settles around 800 rpm. Unless it's incessantly fluctuating that much, it sounds 'normal' to me.

No I’m not talking about a cold start. The issue is when the engine is at normal operating temperatures and I stop at a red light or put it in park with the engine idling. It’s mostly noticeable in park with the engine running though. Everything will be running normal then I will hear(exhaust)/feel power lost or strong like load on the engine. The rpms will drop slightly and I can hear it in the exhaust.

 

[Romclean]

It will happen about every 2-3 minutes sometimes less. Could it be a bad evap purge valve? If so, would it throw a check engine light?

 

[ORRadtech]

Probably not your issue but thought I'd throw it out there.
My EcoBoost would drop idle after filling with gas. It would drop 200ish rpm at idle but never stall.
The dealer replaced the Evap purge valve. It's about a $50 part and an easy swap. Had it not been under warranty I'd have replaced it myself.
Anyway, I know it's not the same engine but the info might help.

 

[Romclean]

I’m going to check that out tomorrow when I get my car back. I bought the car used last year from a ford dealership and didn’t notice this until a month ago. I might end up taking it to the dealership if I can’t figure it out since I have a extended warranty.

 

[Endokendal]

My 2018 does something similar... at idle it will drop RPMs almost to a stall, and then the engine will rev itself slightly to keep from stalling, and then drop back to normal idle. It will do that maybe 2 or 3 times sitting at a stop light. It has never stalled out yet, but it does seem like maybe the idle is set just a hair low and the computer is gunning it a bit to avoid a stall occasionally.

 

[Romclean]

My 2018 does something similar... at idle it will drop RPMs almost to a stall, and then the engine will rev itself slightly to keep from stalling, and then drop back to normal idle. It will do that maybe 2 or 3 times sitting at a stop light. It has never stalled out yet, but it does seem like maybe the idle is set just a hair low and the computer is gunning it a bit to avoid a stall occasionally.

That’s pretty much what I’m experiencing, so this might be normal?

 

[Endokendal]

That’s pretty much what I’m experiencing, so this might be normal?

dunno. curious if it happens to others.

 

[ORRadtech]

A normal idle doesn't fluctuate 200/300 rpm.
Since my purge valve was replaced the idle has been rock steady.
So, no, it's not normal no matter how many others have the issue.

 

[fahadco80]

It will happen about every 2-3 minutes sometimes less. Could it be a bad evap purge valve? If so, would it throw a check engine light?

Hi,

I have the exact same issue, RPM fluctuating when driven hard and come to stop, with hard shifting 4th to 5th only when in sport mode and track (normal mode trans drives great).

First, the dealer did change the CHAIN TENSIONER because I was having other weird noises and that noise never fixed, then I noticed the RPM fluctuation when I come to stop, with few occasions that the car stalled on me and I recorded that on my GoPro and I data logged the RPM fluctuation moment, after showing the dealer the data and the videos, they changed the CAM PHASERS, EVAP, VCT, INJECTORS and TB.

The engine noise fixed, but the RPM issue still there, no stalls yet, but I also think when summer comes, stalling issue will return.

After changing all the mentioned parts, the only parts that I can think of is the OIL PUMP and the IMRC that can be related to RPM.

PLEASE let me know if you managed to fix yours..

Regards

Fahad

 

[DonnieO]

Watch "Gen 3 Mustang Coyote Intake cam idle stumble issues explained." on YouTube


Most likely the same on gen 2

 

[fahadco80]

My 2018 does something similar... at idle it will drop RPMs almost to a stall, and then the engine will rev itself slightly to keep from stalling, and then drop back to normal idle. It will do that maybe 2 or 3 times sitting at a stop light. It has never stalled out yet, but it does seem like maybe the idle is set just a hair low and the computer is gunning it a bit to avoid a stall occasionally.

Can the Forscan adjust the idle?

 

[PonyBoyee]

2017 GT, same exact issue. replaced plugs, coil packs and air filter. (needed anyway)...no change. Very random, does not die when it happens, and never an engine light. Going to reload tune next.

Sponsored