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2020 MUSTANG GT link G4x shutting off randomly


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I have since finally got car all good and running (and dyno tuned) it has been working fine with zero 

issues for 2 months, and out of nowhere it has developed a stange issue with no correlation as to why it happens.


the car will begin to stumble than shut off on its own, as well as the throttle body voltage goes crazy. 

the only thing I have noted with the log fil is that the ignition timing locks at 25 degrees and holds and thats when the car will either stumble or just straight shut off.

any help on where I should start?? the problem will sometimes go away for hours and than randomly come back. 

it does it when cold and when hot.

attached are a few logs.

(vvti has been locked out cam phasers deleted) 

car uses a haltech 8 cylinder ignitor to control ignition. 

also i dont see any errors in trigger scope?? however i am still new to link so i maybe missing something. 


mustang shutting off - 2024-04-17 2_38_13 pm.llgx shutting offTrigger Scope - 2024-04-17 2_48_45 pm.llgx TriggerScopeLog.llg5

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Looks like it just needs more idle position, the idle ignition timing going to 25deg is because the idle speed is getting too low and it is trying to hold the engine speed up, if you give it more idle base position this should both hold the engine speed up and reduce how hard the idle ignition control has to work to hold the engine speed up.

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Looking at your log again and there appears to be some big bumps in the amount of fuel going in just before it dies which appear to be coming from the accel fuel putting in an extra 4ms of fuel which is about 5 times what it's putting in to keep it idling so maybe have a look at your tune and log to see why it is adding so much extra fuel in through the accel enrichment at that point in time.

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Im not sure if this is your only problem but it appears there is something wrong with your MAP sensor or its plumbing - it takes nearly 3 seconds after the engine stops to return to atmospheric pressure.  Prior to that it looked like it was giving normalish response.  Perhaps a kink in the hose or its full of oil or delaminating?


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It was a faulty kill switch, I was running the cartek battery insulator kill switch that isolates the ground. 

I am assuming it was messing with the vehicle ground. When I bypasses the switch all the problems went away. 

so basically a bad ground.


also I was using a very small air hose for Map so I also changed to a bigger diameter hose (didn't make a difference to shutting off) but the response is better.


Nevermind it still does it 

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nevermind it is still doing it, 

The only correlation I see is the ignition timing starts becoming erratic and locks at 25 btdc 

also when its about to shut off even if I floor it the car still shuts off and the code that constantly comes up is code 76 

(I have replaced throttle body already today and it made no change) 

attached is log 

car ran fine for an hour and than problem came right back 

mustangstillshuttingoff pm.llgx

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It appears there is an issue with your TPS main signal.  If you have already replaced the throttle then it would have to be a bad connection to the TPS main sensor somewhere.  The throttle position control uses the TPS main sensor, the TPS sub is only used as a comparison for error checking.  In both of your logs the TPS main gets erratic just before the engine stalls, but if we look at TPS sub it is not erratic and is actually sealed shut at zero.  So it looks like TPS sub is actually the correct one and TPS main is wrong.  

I think that could also explain the MAP signal taking a long time to bleed away the vacuum yesterday as with the throttle sealed shut there would be vacuum produced until the engine completely stopped.  The engine is still actually turning after the log shows zero RPM, this is just the point where the trigger signal is no longer reaching the threshold.   

Since the TPS sub signal looks reasonably realistic I think that suggests the 5V and gnd is probably ok, the issue is more likely with the TPS main signal connection so that is what I would concentrate on first.  I would start by setting up a big gauge on a PC Link screen with TPS main displayed, watch that while yanking/bending/stretching/shaking the loom and connectors around the throttle, ecu, and the path in between.  Hopefully you will see it go crazy when doing that.  

2 hours ago, alexlspec said:

The only correlation I see is the ignition timing starts becoming erratic and locks at 25 btdc 

As Vaughan said yesterday this is just idle ignition control hitting the max clamp trying to keep the engine alive.  


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