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HELP! Idle Consistently Fluctuating and Causing Hesitation 2016 GT Supercharged

nahmed405

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  • I have a 2016 mustang GT with a Vortech v3 supercharger on it tuned by lund.
  • I have left and right upstream O2 sensors, but no cats, and O2 sensors. The only codes I have are for the missing downstream O2 sensors.
  • I have 3 inch long tube headers with an X pipe that goes to a 2 1/2 inch stock GT muffler (I had a uniform, 3 inch exhaust prior and the issue was still there
  • I have 140,000 miles (a lot of highway miles) on the car which is a lot but the car was only supercharged in the last four years/no more than 10,000 miles
  • I have two JLT catch cans and a breather on the intake
Problem
  • Attached is a video of my idle bogging consistently and its on youtube here.
  • When I drive, the car never shuts off from the idle stumbling, but there will be hesitation, and that's the real reason why I want to fix this otherwise, the idle wouldn't really bother me. I have a feeling that they're connected but there's a chance it's not.
  • The idle fluctuation is constant through all rpms because my friend has a code reader, that can set the RPM and my car will consistently bounce between the set rpm.
What I Tried
  1. I did an extensive vacuum leak check with an automotive smoke machine multiple times with no indication of a leak. (Have videos)
  2. I did an extensive vacuum leak check on the exhaust and that is all fixed up now especially the areas near the upstream O2 sensor. (not a single leak in the whole exhaust except for the water weep hole at the muffler)
  3. I changed the spark plugs and make sure they were gaped to lunds recommendation
  4. I replaced the mass airflow sensor with no result so I put the old one back in
  5. I changed the purge valve with no results so I put the old one back in
  6. I changed the fuel sock, even though it wasn't dirty at all
  7. I fixed the IRC intake, runners, and lock them with the tune to reflect that
  8. I changed all 4 vvt solenoids
  9. I replaced both O2 sensors and that helped with the hesitation a lot, but not the idle
Nothing I did in the list above fixed it with the exception of the 02 sensors being replaced and the exhaust leak near the 02 sensors being fixed. It didn't fix the idle but it helped with the hesitation but that hesitation is still there, just not as bad.

Happy to try things like the throttle body and charcoal canister etc but a little logic/testing before I through money at it would be nice. Im open to trying everything though. If I were to guess it would be related to the 02 sensors but I was told that I can be fine without the downstream ones. Anyways Please help!!!

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Zrussian13

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Is the breather on your intake post maf?
 
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nahmed405

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IMG-20240304-WA0007.jpg


Here is a picture of the set up though there was no difference in idle pre and post breather/catch can install.
 

CrackedHorn

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I take it this is a newer issue and didn't just start to happen when you added the Vortech and new tune?

I have had/seen similar issues on other cars where the coil packs were worn out. Not enough to trip a CEL but enough to cause stumble and idle issues.

Weak battery or a weak alternator /bad ground can also cause similar issues. But usually accompanied by other issues.

TPS / EGR can also be at play

Edit to add, my car does something similar when I'm fueling up with the car running. In my case, might be normal or a purge valve issue. But it isn't much an issue for me to mess with right now
 
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nahmed405

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Yup your right. The car had the supercharger installed by previous owner and he said after 6 months it started to have the idle issue.

It was way worse before and I had a cylinder 8 missfire/missfire detected on first 1000 revolutions and but those were both fixed when I changed the bad 02 sensor.

I am going to look into the coil packs since they are an easy install, thanks for the idea.
Any thoughts on how to check the TPS, is it connected to the Throttle body?
Is the EGR your referencing the same as this (evap purge value)
 

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nahmed405

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Just changed the throttle body and the ignition coils (did a KAM reset as well afterwards) and no improvement. HOWEVER, I did find a ton of oil in the intake and behind the throttle body, and a lot on the outlet of the supercharger. I literally just changed the oil 350 miles ago for both the engine (gold color oil) and the supercharger (red color oil) but the oil I found was gray. I am not sure if this is the engine leaking, the supercharger leaking or the evap system is off somehow (IDK much about this sys) but this is where I am at now. Any suggestions?



PXL_20240409_203027147.jpg


PXL_20240409_201118662.jpg


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PXL_20240409_201113071.jpg
 

jpjr501

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That looks like supercharger oil. Does the MAF got oil on it?
 
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nahmed405

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This is the oil from the supercharger on the dipstick and the other one photo. The maf sensor tune was dry and I'm suspecting because the oil had to come from the outlet of the supercharger all through the other pipes and intercooler.

PXL_20240306_175324140.jpg


PXL_20240306_174842022.jpg
 

Torinate

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I take it this is a newer issue and didn't just start to happen when you added the Vortech and new tune?

I have had/seen similar issues on other cars where the coil packs were worn out. Not enough to trip a CEL but enough to cause stumble and idle issues.

Weak battery or a weak alternator /bad ground can also cause similar issues. But usually accompanied by other issues.

TPS / EGR can also be at play

Edit to add, my car does something similar when I'm fueling up with the car running. In my case, might be normal or a purge valve issue. But it isn't much an issue for me to mess with right now
Why are you filling up with the car running??
 
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nahmed405

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Not following your sentence to well but I didn't fill anything up yesterday and the car wasn't running.
 

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Torinate

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Not following your sentence to well but I didn't fill anything up yesterday and the car wasn't running.
No. That was for @CrackedHorn
He said he had this issue when he fills up with the car running.
 
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nahmed405

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Lol oh I see. Lol yea don't fill up with the car running lol
 
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nahmed405

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I ended up isolating the oil leak to be from the supercharger. The supercharger is off of the car now and is going to be sent back to be repaired. In the meantime, I have the serpentine belt bypassing the supercharger, and the car is basically stock now. HOWEVER, I still have the same idle issue, which means I can rule out the supercharger from being the cause. This is the first time I've heard the engine run without the supercharger, and I noticed it have a loud ticking noise from the engine, but I don't know if that's normal or not. I was looking into some forums and people were saying that it might be a dirty fuel injector or my cam phasers(I changed out the VVT solenoids, but not the phasers). Does anybody have a thread that they can link about cam phasers, dirty, fuel injectors, or engine tick? If anyone has a video of how a car might run with a bad phaser or dirty fuel injector that might help me rule some possibilities out as well.

Thanks for the help so far and stay posted if you are interested in the fix!
 

CrackedHorn

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I ended up isolating the oil leak to be from the supercharger. The supercharger is off of the car now and is going to be sent back to be repaired. In the meantime, I have the serpentine belt bypassing the supercharger, and the car is basically stock now. HOWEVER, I still have the same idle issue, which means I can rule out the supercharger from being the cause. This is the first time I've heard the engine run without the supercharger, and I noticed it have a loud ticking noise from the engine, but I don't know if that's normal or not. I was looking into some forums and people were saying that it might be a dirty fuel injector or my cam phasers(I changed out the VVT solenoids, but not the phasers). Does anybody have a thread that they can link about cam phasers, dirty, fuel injectors, or engine tick? If anyone has a video of how a car might run with a bad phaser or dirty fuel injector that might help me rule some possibilities out as well.

Thanks for the help so far and stay posted if you are interested in the fix!
You can try giving this a read.

https://www.mustang6g.com/forums/threads/rpm-drops-on-2019-gt.175505/page-4
 

Whitedevil95

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Sounds like its time for a compression test.
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