Roush Stage 3 low idle/ chugging sound

[2017-RS3]

Hey Guys, new to the forum. I have a 2017 Roush Stage 3 on stock tune. Only upgrades are a VMP Triple pass heat exchanger with Dual fans, K2 air filter from Palm Beach Dyno and oil catch cans. I have noticed when the car is warmed up the RPMs drop to about 500-550 and the exhaust makes a chugging/ loping sound like its missing and the exhaust note becomes almost non-existent/silent. From what i have read, most S550s stay at about 700 rpms at idle. Car has 4,300 original miles. I changed the plugs to NGK 6510's and gapped to .030. No change in idle. One thing I noticed is the RPMs increase about 1-200 when I press the clutch in and it sounds normal. As soon as I let the clutch out in neutral RPMs drop back down to about 500. I have ran a few tanks of Boostane in the car because we only get 91 octane and race gas is $15/gal here. Anyone else had this issue? Are the dual fans drawing too many amps, Boostane clogged cats/O2's, or oil from the Air filter made the throttle body dirty? Going to clean the MAF sensor today and see if there is a change. Any help is appreciated.

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[KingKona]

You're gonna' hafta' clarify this;

....on stock tune...

....before help can be provided.

 

[Zrussian13]

Not sure what your issue is but I doubt it's from running few tanks of boostane. I'm also on az shitty gas so I've been running 8-16oz of boostane in every tank for the last year and a half (30k miles) with no issues. Well other than having to change or clean my spark plugs every 10k miles. This is what they look like at 10k.

 

[Schnder95]

Rough superchargers say never use octane boosters with there superchargers. 93 only. Others I don't know.

 

[2017-RS3]

You're gonna' hafta' clarify this;



....before help can be provided.

Stock phase 1 tune from Roush.

 

[2017-RS3]

Not sure what your issue is but I doubt it's from running few tanks of boostane. I'm also on az shitty gas so I've been running 8-16oz of boostane in every tank for the last year and a half (30k miles) with no issues. Well other than having to change or clean my spark plugs every 10k miles. This is what they look like at 10k.

Mine were definitely orange/ red but not that bad. I was only using about 3oz per fill-up of the professional just to put me at about 93-95 octane.

 

[Nodster]

Didn't someone recently have an issue with their supercharger (when coming to a stop) almost stalling and a low idle? But driving was OK. Wasn't it a duff ignition coil?

Quick test for the MAF - just unplug it when car is sitting at idle. If it runs the same / no noticeable change, or runs better, then the MAF is the issue. Could also be a leak on an intake or a hose somewhere meaning excess air is messing up the readings past the MAF.

 

[2017-RS3]

Is it normal for gen2 coyotes after car is warm to idle at 550rpm? The sound I'm hearing is like a low thump sound intermittently but only when car is in neutral/ clutch out and the RPMs sit steady at about 550. If I'm at a stoplight with the clutch in, the RPMs are steady at about 700 and I don't hear the sound.

 

[2017-RS3]

Didn't someone recently have an issue with their supercharger (when coming to a stop) almost stalling and a low idle? But driving was OK. Wasn't it a duff ignition coil?

Quick test for the MAF - just unplug it when car is sitting at idle. If it runs the same / no noticeable change, or runs better, then the MAF is the issue. Could also be a leak on an intake or a hose somewhere meaning excess air is messing up the readings past the MAF.

Didn't someone recently have an issue with their supercharger (when coming to a stop) almost stalling and a low idle? But driving was OK. Wasn't it a duff ignition coil?

Quick test for the MAF - just unplug it when car is sitting at idle. If it runs the same / no noticeable change, or runs better, then the MAF is the issue. Could also be a leak on an intake or a hose somewhere meaning excess air is messing up the readings past the MAF.

Just cleaned the MAF sensor. I'll see if it's still doing it. Car drives fine. I just want to make sure there isn't an underlying issue as I drive the car hard when I do drive it. This is my first mustang with a coyote so it may just be the nature of the engine and I'm tripping.

 

[Nodster]

I'm going out in about an hour, so I'll see what mine idles at as I have no idea off the top of my head.

 

[2017-RS3]

I'm going out in about an hour, so I'll see what mine idles at as I have no idea off the top of my head.

Do your RPMs drop about 150 when you let off the clutch in neutral then raise back up when you press it back in?

 

[Nodster]

So cold start, up to 1,300rpm. Settles to 1,000rpm. Then yeah, bang on 700rpm at idle when I was using the car and stopping at lights etc. No where near down 500rpm.

 

[Nodster]

Do your RPMs drop about 150 when you let off the clutch in neutral then raise back up when you press it back in?

It's auto mate sorry. I can't replicate that for you.

 

[2017-RS3]

So cold start, up to 1,300rpm. Settles to 1,000rpm. Then yeah, bang on 700rpm at idle when I was using the car and stopping at lights etc. No where near down 500rpm.

Damn. Okay. Mine stays at 700 after cold start while the temp is "Low" and as soon as it hits "normal" drops down to about 550 and that's where I'm hearing that chugging sound from the exhaust.

 

[2017-RS3]

Damn. Okay. Mine stays at 700 after cold start while the temp is "Low" and as soon as it hits "normal" drops down to about 550 and that's where I'm hearing that chugging sound from the exhaust.

I don't know much about how manual transmission clutches work but it seems like it is causing slight pressure when the clutch is out and causing the RPMs to drop slightly and the chugging noise is just low rpm idle and the motor trying to compensate and catch itself so it wont stall. Better than a misfire I guess. I know the Mt82 isn't meant for the amount of torque the superchargers add.

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