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HELP! Idle Consistently Fluctuating and Causing Hesitation 2016 GT Supercharged

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nahmed405

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Sounds like its time for a compression test.

Lol the dreaded test I didnt want to do was done. These are the results:

195, 210, 210, 210, 195 190, 200, 180.

Cylinder 8 was the last one with 180psi and that might be the culprit. But I did a leak down test right after and it sounded the exact same as when I did it from a good cylinder.

Here is the good cylinder results
Here is cylinder 8 results


I was reading the forums that CrackedHorn sent and the thing that I think is closely related to my issue is a cam phaser. I had this on my list to check out but I am hesitant since it is a pricy fix and the way people describe their symptoms, it doesnt exactly match mine idle issue since it happens all the time with slight fluctuation, not randomly and abruptly.

Crankshaft position senor is also something I will look into after reading the forums but what do you all think about these numbers for compression. I was reading another post about it and couldn't get a definitive answer if this was normal.
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Total shot in the dark here but did you try a KAM relearn and crank relearn?

Admittedly I'm just throwing spaghetti at the wall, but there shouldn't be any harm in doing so.

If your fuel trims look good and you aren't finding a vacuum leak, it's worth a shot.

Compression numbers should generally be within ~10% of eachother from what I've always been told. The number itself doesnt matter too much unless it's really low as all gauges read differently. My compression was 212 on all cylinders except with #5 being 240, for instance. No idea why. Probably carbon.

Someone on the forum told me that the Ford workshop manual says within 25% of the lowest and highest Is acceptable. Which sounds awful high to me, but I'm no expert, either.

By both metrics, your compression seems to basically be within range as far as I can tell.
 
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nahmed405

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Total shot in the dark here but did you try a KAM relearn and crank relearn?

Admittedly I'm just throwing spaghetti at the wall, but there shouldn't be any harm in doing so.

If your fuel trims look good and you aren't finding a vacuum leak, it's worth a shot.

Compression numbers should generally be within ~10% of eachother from what I've always been told. The number itself doesnt matter too much unless it's really low as all gauges read differently. My compression was 212 on all cylinders except with #5 being 240, for instance. No idea why. Probably carbon.

Someone on the forum told me that the Ford workshop manual says within 25% of the lowest and highest Is acceptable. Which sounds awful high to me, but I'm no expert, either.

By both metrics, your compression seems to basically be within range as far as I can tell.
Phew! Was really stressing the compression numbers since I did it.

I did both the KAM relearn and crank relearn. No result.

On my list of parts to throw at this is:
  1. Fuel injectors /cleaning
  2. Crank position sensor
  3. Camshaft position sensor
  4. Cam phaser
I'll be all out of things to try after that lol. I'll do this soon hopefully.
 
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nahmed405

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Update:

Changed the fuel injectors to stock injectors and also the tune since it would not run on the aftermarket injectors. No change in rpm fluctuation but definitely noticeable improvement in getting rid of the hesitation. However, the rpms would really do some weird things like hang at 1200 rpm randomly. Not every single drive but enough to know its not a permeant solution or something I can live with. I ended up cleaning my aftermarket injectors professionally and they unfortunately said that the injectors were in perfect condition from their tests. Although the stock injectors made the car drive much better (not the idle but def the drive), I had to also change the tune so I am not sure the injectors was the fix since there was 2 variables. Also the idle wasnt fixed so I am not sure what to make of that. The previous owner said that the car was driving great and then one day the idle was off and hesitating and this was 6 months after the lund tune so its hard to think that code can go bad but rather a physical component. He said it was an o2 sensor and when I changed that the car drove significantly better since then but still not livable.

I also changed both the intake and exhaust camshaft position sensor on both sides and the crankshaft position sensor.
  1. Fuel injectors /cleaning
  2. Crank position sensor
  3. Camshaft position sensor
  4. Cam phaser
Last thing to try is the Cam phaser. Not too excited about this one but I'm out of options after this.
Any advice on a in person would also be helpful if there is one.

Thanks for reading!
 

Miked81

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So my 17 did the same thing when I first got it I have a Paxton on mine. But it had missfire at start up would not stay idling. If you drove it no problem. But at a stop light it would die. Turned out there was bad gas in the car. It was also at a time when gas stations switched from summer to winter blend. And apparently this is a common problem for fords. Ran the tank out an added a can of octane boost an by the second fill up the issue was gone. I was going crazy thinking it was a possible cam phaser issue also. I even bought them. But I did not have a tick your compression numbers are good but you may have a valve problem. Or an exhaust leak it’s hard to say without hearing it. Sometimes exhaust leaks sound like ticks. An if the leak is near where an o2 sensor is located it will cause problems.
 

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nahmed405

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So my 17 did the same thing when I first got it I have a Paxton on mine. But it had missfire at start up would not stay idling. If you drove it no problem. But at a stop light it would die. Turned out there was bad gas in the car. It was also at a time when gas stations switched from summer to winter blend. And apparently this is a common problem for fords. Ran the tank out an added a can of octane boost an by the second fill up the issue was gone. I was going crazy thinking it was a possible cam phaser issue also. I even bought them. But I did not have a tick your compression numbers are good but you may have a valve problem. Or an exhaust leak it’s hard to say without hearing it. Sometimes exhaust leaks sound like ticks. An if the leak is near where an o2 sensor is located it will cause problems.
Very helpful, I'll give it a shot. How did your car idle, did it go up and down consistently like here or more of a stall at a red light.

Also the engine tick was just my injectors operating normally. I definitely had an exhaust leak near my o2 but I fixed that and it helped a lot, the whole exhaust is air tight now.
 

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I think you're chasing your tail here with the idle thing. Maybe a good tuner could make it a little more stable, idk. If you have hesitation, it's something else, not related to the idle. For an example, here's a log of my car with a Whipple showing rpm and the AFR from the O2 sensors.

idle 325.PNG


That was with a 3.25 pulley. Here's an old log from a 3.625 pulley, so it looks like more airflow from the smaller pulley makes it a little more obvious.

idle v3.PNG
 

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Very helpful, I'll give it a shot. How did your car idle, did it go up and down consistently like here or more of a stall at a red light.

Also the engine tick was just my injectors operating normally. I definitely had an exhaust leak near my o2 but I fixed that and it helped a lot, the whole exhaust is air tight now.
It would idle like I go #2 after drinking all day an hitting Taco Bell which is out of control 🤣 but no seriously it would stick high then go way down a stall out. Was very random. I stressed myself out basically over bad gas. Sometimes you get lucky and it’s a simple fix.
 
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Yea i'll try the bad gas thing, I did run the tank empty once and had to fill with the gas cans but it wont hurt to try again.

@Ruiner46 When I took it to the tuner he said 800 bucks to take a look at it because he couldn't work with lund's tune and needs me to get an stc tuner. He also said he would spend a a few days on it and probably couldnt get the idle to be significantly better since it is only fluctuating around 50rpm. He drove the car and felt the hesitation and said its noticeable but slight. Very nice guy and spent hours with me just brainstorming but at the end of it he said try some simple stuff before spending big bucks with him for a chance that its not going to be much better.
 

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Can you do a power balance test and see if cylinder 8 is low? Compression is lowest in that one and it's commonly one that dies...
 

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I think you're chasing your tail here with the idle thing. Maybe a good tuner could make it a little more stable, idk. If you have hesitation, it's something else, not related to the idle. For an example, here's a log of my car with a Whipple showing rpm and the AFR from the O2 sensors.

idle 325.PNG


That was with a 3.25 pulley. Here's an old log from a 3.625 pulley, so it looks like more airflow from the smaller pulley makes it a little more obvious.

idle v3.PNG
Doesn't seem like the pulley should affect anything idle because of the bypass valve
 
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nahmed405

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Can you do a power balance test and see if cylinder 8 is low? Compression is lowest in that one and it's commonly one that dies...
Whats that, how do I go about doing that
 
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Update, I drained the gas tank and visually inspected it and no water or debri was found. Also I got the supercharger back in when it was serviced/repaired for the oil leak. It still drives the same. I randomly had my traction control and abs lights go off and is now dissabled, not sure if it is connected but I know I read up on traction control being turned off to help with hesitation. But thats not the case with me because its off and still hesitates. I assuming this is a ground issue or sensor issue but I strongly feel they are unrelated.

Last thoughts are power balance test and cam phaser replacement.

@Ruiner46 I reread your post but still am confused on what you are suggesting
 
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I just learned how to pull logs and am posting the results of an idle log where I was able to capture a bounce in the idle. I have an excel attached but here is more context:

  • The whole log has a fluctuating idle but at one point it bounces more noticeably
    • My graphs focus on this bounce to since I believe it is highling the problem
  • Highlighted red means the number is negative
  • Highlighted green means the number is positive
  • The red text indicates a snapshot of that bounce
  • the Large text indicates when I think the bounce happens
If someone has a normal idle parameters it would be helpful if you can post so I can see whats off.
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