2017 GT350R Troubling Engine Misfire

[HR300]

Hi,
I am the original owner of a 2017 GT350R. Been experiencing engine misfire codes for a few months - I have other cars and truck so do not
routinely drive the car but generally do drive the car once a month or more for grins.

A short summary about this car.
All stock, with about 14,000 miles, of which about 4,000 of those track miles. Car has been well maintained. Ford replaced transmission under an extended warranty, and clutch was replaced too which I paid for - this was at around 12,000miles. Car is now out of warranty. No other problems.

I am asking for comments concerning the solution that currently my mechanic is recommending to cure this misfire problem. So I will outline the misfire codes
and items that were checked.

Primarily, the misfire code has been PO307 which is for Cylinder 7. Though there have been PO300 a couple times and PO304 at least once. Especially,
PO307 code appeared 6 or 7 times after clearing and resulting in CEL remaining on. I could never feel the engine misfire or detect a change in performance
or engine sound, and neither could my mechanic. Engine misfire codes appeared on moderate acceleration from about 3000 - 4000 rpm. Car started and
idled as normal.

Items that have been checked:

1) A couple new tanks of gasoline (93 octane) and one additional bottle of fuel system cleaner/additive.
2) Switching out Cylinder 7 spark plug and coil - but misfire code stayed on P0307. Plugs and coils appeared in great condition.
3) Cleaning and flow testing all fuel injectors - all normal.
3) Compression and leak down tests - normal.
4) Checking the wiring signals to the ECU, were normal.
5) Inspection of internals (valves etc,) Cylinder 7 with borescope as mechanic thought perhaps there could be failures beginning even though compression
and leak down tests were normal.

6) NOW - my mechanic is telling me the misfire problem has been pinpointed as faulty injector drivers from Cylinder 4 and 7 registering negative voltage and
recommends replacing the ECU and programming of ECU. I have not discussed this yet with my mechanic but I have trouble understanding how this could be
happening as it seems this would result in no fuel going to those cylinders which seems like it would major major noticeable.

Appreciate comments / recommendations. A comment about my mechanic - he has a great shop and been in business working on high end cars and trucks - works on mustangs because he has owned and raced a few of them and I have been going to him a few years with a couple of my cars.

Thanks for any help.

Karl

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[Inthehighdesert]

Did he check the harness on top of the motor really well. Mine had similar when I was dynoing it arter the fi Install. We found some bad connections and issue’s in the harness. It was intermittent till we started really moving it around and finding where the issue’s were. The car at the time had 1200 miles on it. Chasing an electrical issue can be tedious and time consuming. Not a particularly fun thing to have to do.

 

[HR300]

Did he check the harness on top of the motor really well. Mine had similar when I was dynoing it arter the fi Install. We found some bad connections and issue’s in the harness. It was intermittent till we started really moving it around and finding where the issue’s were. The car at the time had 1200 miles on it. Chasing an electrical issue can be tedious and time consuming. Not a particularly fun thing to have to do.

Thanks for the comment.
My mechanic said he has checked all the connections but I will bring it up to him. Replacing the ECU and reprogramming would seem to be unnecessary, and if this item with negative voltage to the two fuel injectors was going on seems like some other code would show up also.

 

[Inthehighdesert]

I don’t see how replacing the ecu will help. I’d be very surprised if there was an issue there. The reflash isn’t a big deal as long as its the oem flash. That doesn’t hurt anything to do. Mine wasn’t throwing codes when it was having that intermittent issue. In my case I’m sure the fi install was what brought the issue out sooner then later.

Thanks for the comment.
My mechanic said he has checked all the connections but I will bring it up to him. Replacing the ECU and reprogramming would seem to be unnecessary, and if this item with negative voltage to the two fuel injectors was going on seems like some other code would show up also.

 

[526 HRSE]

Sounds like a computer/wiring issue. Maybe it's been there longer than you know. What caused a transmission replacement at such low miles?

Of course electrical issues can be a nightmare. Had a VW GTI back in the day that took about 8 months to diagnose. Turned out to be a faulty connector.

 

[ice445]

Idk about the gt350 specifically but any time you replace a clutch you're supposed to do a misfire profile correction relearn. Given you don't notice anything it may just be that needs to be done.

 

[HR300]

Sounds like a computer/wiring issue. Maybe it's been there longer than you know. What caused a transmission replacement at such low miles?

Of course electrical issues can be a nightmare. Had a VW GTI back in the day that took about 8 months to diagnose. Turned out to be a faulty connector.

Thanks for the comment.
In reply to what caused a transmission replacement at such low miles I do not know for sure but I was "hard" on the transmission during some of my track events was likely the cause.

 

[HR300]

Idk about the gt350 specifically but any time you replace a clutch you're supposed to do a misfire profile correction relearn. Given you don't notice anything it may just be that needs to be done.

Thanks for the advice. I have seen this item mentioned in searches and even saw a note that Ford was supposed to note the relearn process was done on the work receipt, but there are no notes about this from the Ford transmission/clutch/flywheel replacement.

I will do some searches on how to do the misfire profile correction but if you can refer me to the procedure be much appreciated.

 

[CANTWN4LSN]

Know next to nothing about electrical issues. But with 4000 track miles and engine misfire codes there have been previous posts about coil pack issues perhaps heat related and fix by replacing harness. See @honeybadger's posts on this issue. May be helpful.

 

[Mach VII]

Thanks for the advice. I have seen this item mentioned in searches and even saw a note that Ford was supposed to note the relearn process was done on the work receipt, but there are no notes about this from the Ford transmission/clutch/flywheel replacement.

I will do some searches on how to do the misfire profile correction but if you can refer me to the procedure be much appreciated.

https://www.mustang6g.com/forums/th...s-weird-hesitation.125119/page-2#post-2679084

 

[ice445]

Thanks for the advice. I have seen this item mentioned in searches and even saw a note that Ford was supposed to note the relearn process was done on the work receipt, but there are no notes about this from the Ford transmission/clutch/flywheel replacement.

I will do some searches on how to do the misfire profile correction but if you can refer me to the procedure be much appreciated.

Mach VII posted it, you can do it with forscan/forscan lite and an mscan supported adapter as well. I'd try that and see if they go away.

 

[TommyBoyDIY]

The code isn't right but I just had issues with the fuel rail pressure sensor on my 2016 and then the battery died too. Replaced both and now working fine. But was having weird engine hesitation prior to changing. The code that finally came up though was P0088 I believe

 

[95CobraR]

I say anyone that has raced any car for 4000 miles needs to understand that all race cars should be rebuilt at least every two years.

Your car failed from an obvious lack of maintenance as a track car. You need to learn how to do it or hire a good track mechanic to help you.

 

[HR300]

An update on my Cylinder 7 & 4 misfire. The misfire problems have been eliminated or corrected by installing a new / replacement ECU, per my mechanics recommendation and analysis. Each of the fuel injectors are controlled by a "major signal" and "minor or trim signal" from the ECU and the problem was the signal from the ECU was lacking or "negative" for the minor signal which is finally controlled by a hardware piece (a chip or capacitor) in the ECU and when this happens have to replace the ECU.

Anyway I have had the car out 3 different times driving thru the rpm range and past 100 mph for a total of about 150 miles and car running great with no misfire or other cell codes.

Certainly hope no one else has this problem.

 

[ice445]

An update on my Cylinder 7 & 4 misfire. The misfire problems have been eliminated or corrected by installing a new / replacement ECU, per my mechanics recommendation and analysis. Each of the fuel injectors are controlled by a "major signal" and "minor or trim signal" from the ECU and the problem was the signal from the ECU was lacking or "negative" for the minor signal which is finally controlled by a hardware piece (a chip or capacitor) in the ECU and when this happens have to replace the ECU.

Anyway I have had the car out 3 different times driving thru the rpm range and past 100 mph for a total of about 150 miles and car running great with no misfire or other cell codes.

Certainly hope no one else has this problem.

I'd replace those injectors on those problem cylinders as well. Any time an ECU driver or circuit gets fried I'd suspect an issue with what that was controlling. Two injectors are cheap and worth the peace of mind imo

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