2020 GT misfire issues

[AlmostHeaven]

New member here, not new to forums or Fords, and looking for some advice.

The little lady's 2020 GT PP1 has some misfire issues that the dealership(S) cannot diagnose.

Car currently has Roush CAI, resonator delete, and H Pipe. No tune yet. 8000 miles on the clock. The car has driven an average of 5 miles a day.

Initial issues were related to a hot start. Drive it a short distance, park it, restart it and it acts like it's difficult to crank, misfires a bit without codes, stumbles, and then comes to life. Seemed to be worse in warmer weather. Very rarely in that instance, it would stall. Cold starts in the morning are violent and beautiful. The dealer told me I would need to pay them to remove the Roush CAI, installed by a Roush Ford Dealer to diagnose. I also confirmed through the dealer it was not fuel related. Felt to me like the fuel rail pressure was bleeding off. I know if my f150 sits long enough it primes the fuel system when you open the door. Thought maybe enough time was not passing and the system was bleeding down. They said no. Wasnt a huge deal, told them I'm not paying them to remove the CAI back to stock.

Drove it for a few months and it started throwing misfire codes with no noticeable driveability issues. Took it to another dealer. Two weeks later and many miles they could not recreate the issue. They recommended I install the Roush tune as they thought that may help. Still have yet to install the tune. Roush says you don't need the tune with the standalone CAI> CODES 0300 and 0301

Started the car in the driveway. Good start, put it in reverse and it was a missing bucking piece of crap. Burping and shaking, put it back in drive and it settled down. Put it back in reverse and more or the same. Turned it off and back on and it went away.

I am baffled. Any thoughts? Also, I have Forscan and use it to mod my F150. Thinking I could hook it up to the mustang and data log a bit. Does anyone know if Forscan will allow me to do that?

BK

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[KingKona]

Re-install the OEM CAI, and make sure there's no vacuum leaks.

 

[AlmostHeaven]

I haven't heard any leaks and the vac gauge pulls hard on the dash under the throttle. I figure I can throw the intake back on. Have to dig it out of storage though.

 

[GilmourD]

Does the idle ever sit around 2000?

 

[AlmostHeaven]

Does the idle ever sit around 2000?

never. once it's up and running it's like nothing ever happened, all the way up to WOT.

 

[AlmostHeaven]

Does the 2020 still have the flaps in the intake manifold? Could that be something to look for?

 

[KingKona]

It's possible the intake manifold was cracked when the CAI was installed, and un-metered air is getting in.

 

[GilmourD]

It's possible the intake manifold was cracked when the CAI was installed, and un-metered air is getting in.

That was my thinking with asking if the idle sits high, like at 2K. Previous owner of my '15GT put a C&L Race CAI on the car and it wasn't until recently that I really properly tightened all the silicone couplers, so every once in a while one would come loose and suck air after the MAF. Once it came loose enough that if I pushed the clutch in while at speed the car would just stall. Real PITA.

 

[KingKona]

That was my thinking with asking if the idle sits high, like at 2K. Previous owner of my '15GT put a C&L Race CAI on the car and it wasn't until recently that I really properly tightened all the silicone couplers, so every once in a while one would come loose and suck air after the MAF. Once it came loose enough that if I pushed the clutch in while at speed the car would just stall. Real PITA.

I haven't heard about GEN3 motors having the issue, but GEN2 Coyotes ate intake manifolds where the metal rods run in them for the throttle body or whatever.

I'm guess it's a weak-spot, and installing a CAI or just changing the air filter (which is a real PITA and puts stress on the intake manifold) cracks it.

Then you get misfire codes all the time.

 

[AlmostHeaven]

Well, that's all disconcerting info. I will check the connections on the intake and look for any leaks. It is going to another dealership tomorrow. If that fails it goes to Tindal Ford which installed the intake and they can sort it out.

 

[AlmostHeaven]

I picked it back up from the dealer. They claim a fouled spark plug. However, it still has the hot start stumble. Guess I need to take it back. Sheesh.

 

[GilmourD]

I picked it back up from the dealer. They claim a fouled spark plug. However, it still has the hot start stumble. Guess I need to take it back. Sheesh.

As a PC technician I'm gonna throw an odd one out at you.

Unplug and reconnect all your coil packs. You may have one that's not connecting right in a certain temperature range due to not being pushed in correctly or some sort of schmutz on the contacts.

I know it sounds dumb, but I've had more than one PC that WOULD NOT even power on let alone properly boot until I pulled the CPU and reseated it. Sometimes reseating something electrical/electronic is a simple, free fix.

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