2017 Mustang GT misfiring under part throttle

[tuneguru]

I'm banging my head with this 2017 Mustang GT I tuned. I dialed it in for pump gas before tuning for e85. The car was running perfectly fine for a few days and then it started having misfires only under part throttle in the 2k-3k rpm range. I datalog the car on pump gas and I see the misfire counter detecting misfires, the spark gets greatly reduced, but it is not being reduced by any knock activity. When I look at the mapped points being referenced they do not call for the timing that the computer is commanding and adjusting to. As soon as the car misfires the fuel system goes from closed loop to open loop fault. I have verified the operation of the spark plugs, coils, maf, and injectors.

The vehicle came installed with an aftermarket manifold that disables the manifold runners. I have them disabled in the tune but is it possible those runners are stuck open?

Any kind of suggestion would be greatly appreciated.

Vehicle Mods: PMAS Intake, Deatschwerks 50lb injectors, LT Headers, Manifold

Datalog: Stutter Correction.hpl
Tune File: 24. Stutter Adjustment.hpt

[Thatwhite5.0]

Disable them in the tune under Airflow > IMRC Switch and Position Sensor set both to "Disabled".

Also in Airflow > Electronic Throttle > Shuffle Switch set to "Disabled" as well.

What do you mean the runners are stuck Open? If they have an IMRC delete they should be opened. You don't want them stuck closed WOT, but your datalogs show them running in IMRC closed mapped points. Open up the scanner and add new channels to your list. Type in "source" and add all of the sources to your channels.
T

[Thatwhite5.0]

Is this going to be an E85 car only or are you planning on switching between fuels?

[tuneguru]

Disable them in the tune under Airflow > IMRC Switch and Position Sensor set both to "Disabled".

Also in Airflow > Electronic Throttle > Shuffle Switch set to "Disabled" as well.

I could have sworn I had those disabled. I will try this and see if it fixes the issue.

[tuneguru]

Is this going to be an E85 car only or are you planning on switching between fuels?

The client wanted a flex fuel tune where he can switch between pump gas and e85

[MRRPMBRP]

Make sure plugs are actually good, no grounds or electrodes broken. I've had it happen, electrode broke off, had a .150" plug gap, ran bad, blower setup, installed new plugs, picked up 150rwhp it was so bad.

[tuneguru]

Thanks for the suggestion MRRPMBRP. I confirmed each plug and checked gaps. Just to be sure got a set of new plugs from Ford dealer and it didn't change a thing. I think Thatwhite5.0 hit the nail on the head. I will confirm tomorrow.

[veeefour]

Do not disable the IMRC - leave them stock. It will use different MP's with IMRC disabled and your torque model will be altered.
If your IMRC is ON but you get the DTC related to IMRC it will yet again use a different set of IMRC's and it will disable KNOCK advance and always stay in BASE spark.

Disabling IMRC gives nothing more but trouble - the only reason you would ever want to delete the IMRC is under moon boost as they can be sucked in. Other then that - leave them ON.

I believe you have a 2018 intake mani swap with IMRC delete? This is beyond me as IMRC delete plates cost 50 USD and adapter harness for IMRC cost 70 USD but people like to cheap on everything.

[tuneguru]

I disabled the IRMC and it made zero difference. Vehicle goes into fuel system fault after a sequence of misfires. It only occurs at part throttle around 3k.

Datalog:IRMC Disable.hpl

[murfie]

If the car has extensions on the O2 sensors, eliminate them. If it doesn't, try new O2 sensors.

[veeefour]

Your STFT goes to over 35% so something must be waaay off in your fuel calibration...this for example...fix your MAF voltage.

Stutter.jpg

[SultanHassanMasTuning]

^Maf period adjust dont touch voltage table

[veeefour]

^Maf period adjust dont touch voltage table

Sometimes you do have to change the voltage table.

[tuneguru]

The car does not have o2 extenders, I know the wide-band sensors don't like the extenders on them. I am reluctant to try new o2's because these only have 20k on them.

For my MAF voltage and period tables, I used the values provided by PMAS. They provided more data than the tables had rows so I did omit a few data points. You guys might be on to something though with the MAF adjustment.

I noticed my STFT's were way out of whack. I adjusted them accordingly, got less misfires but I am still getting misfires. I am going to focus on the MAF period tomorrow and see if that is the cause of the issues.

[murfie]

Are you adjusting your MAF with FF enabled?
Pmas maf transfer shouldn't need to be touched.
I suspect your inferred FF logic isn't working, as the cause of your fuel trims doing what they are. That is why my guess is an 02 problem. Could be a fuel pump controller issue as well.

[tuneguru]

Pmas maf transfer shouldn't need to be touched.

PMAS transfer function has 39 rows of data for the MAF voltage table. The table in the tune has only 30 rows of data.

Are you adjusting your MAF with FF enabled?

I initially dialed in the MAF with FF disabled.

[tuneguru]

Drained the tank of e85, disabled FF, dialed in the MAF on pump gas (91 out in CA), and the car is still misfiring.

It only misfires at part throttle between 3500-4000 rpm. It only misfires in MAF periods 231 thru 279.

adjusted the curve so my STFT are within +/-5% and it still misfires in the same range.

Datalog: PMAS Part Throttle STFT.hpl
Datalog: PMAS Part Throttle STFT 4.hpl
Tune: 32. MAF Play.hpt

[kevinhen]

Can you data log the spark source? trying to see how much timing is being pulled.

[tuneguru]

Can you data log the spark source? trying to see how much timing is being pulled.

Spark Source shows base

Spark Source.hpl

[tuneguru]

Can anybody shed some light on the fuel pump commanded dc? Is it same as fuel pump duty cycle? I tried increasing my max duty cycle to 60% but during the part throttle run my commanded dc is constant around 30%