Possible faulty injector driver?

serfma

New Member
May 1, 2020
5
0
1
27
Kentucky
96 Cobra 4.6 4v, have had a longstanding intermittent issue where I have power issues / cutting out at over 6k rpm. Video of the issue with fuel pressure test: 1st gear, half throttle or LESS pull
View: https://youtu.be/Uji7Ox0ioSI
You may have to turn up the volume to really hear the slight-to-moderate cut outs at 6k-ish or so RPM.

I have either verified, or replaced the following in the last year:

In the last 1 - 2 weeks:
- Fuel pressure OK
- Fuel pump strainer
- Fuel tank entirely pulled and cleaned
- Fuel rails pulled and cleaned
- Fuel pressure regulator
- Fuel filter
- Fuel pump 12v power is solid
- Fuel pump flow test at rails (right around 1 gal from supply line, half a gal from rail at return)
- New injectors (60# with tune) cleaned and flow tested (redneck style)
- Plugs brand new, NGK TR55, gapped at .054" but dropping gap to .035" after tonight.
- Coil packs from Autozone, duralast iirc
- Battery (completely died, replaced)
- MAF (for testing original MAF)
- Air filter
- Tested and verified NO intake leaks
- Found out my rings are RIP lol
- Cam and crank pos sensors replaced
- Custom tuning by well known mustang tuner

In the last 3 - 6 months:
- Alternator, from LMR
- Alternator power wire
- O2 sensors, replaced them with brand new ones the other day to verify their integrity, checked good so put back old.
- Plug wires, motorcraft 8mm
- Dropped k member to replace exhaust manifold gaskets in case of exhaust leaks
- Removed EGR, capped everything off, tuned out
- Aquired Moates Quarterhorse and mounted on ECU
- Walbro 255lph pump

Now that has lead me to digging deeper and I do not know where to turn to for knowledge on ECU related things such as injector driver that I am suspecting next. I recently aquired a uScope that I'm going to check the injectors with during the 6k+ window where break ups happen. I have video proof of fuel pressure being steady during the window, which I am replicating in 1st gear at half throttle or less. (
View: https://youtu.be/Uji7Ox0ioSI
)

This issue only happens at heavy load 6k+ RPM and is intermittent. It is not the same pattern every time. After replacing crank + cam sensor, which is purely coincidence, I had a smooth RPM up to redline. The very next one had slight cut outs. Does anyone have any other ideas, and can help educate on the ECU some? Thanks in advance.
 

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor
Admin Dude
Jan 4, 1985
33,287
15,098
234
Box behind Walmart
www.stangnet.com
The first thing that comes to mind as I watch your video is the possibility that the spark is being blown out. I don't know that I've ever seen this happen on a N/A car (no mention of boost above).

I might try closing up the gap on all the plugs and testing again. If there's any change, you might consider a component that keeps your coils saturated (like a Boost-A-Pump).

You might also try testing the voltage to the coil. If you are seeing a significant voltage drop as RPM rises then your coils are not being saturated.


Welcome aboard and good luck.
 

serfma

New Member
May 1, 2020
5
0
1
27
Kentucky
The first thing that comes to mind as I watch your video is the possibility that the spark is being blown out. I don't know that I've ever seen this happen on a N/A car (no mention of boost above).

I might try closing up the gap on all the plugs and testing again. If there's any change, you might consider a component that keeps your coils saturated (like a Boost-A-Pump).

You might also try testing the voltage to the coil. If you are seeing a significant voltage drop as RPM rises then your coils are not being saturated.


Welcome aboard and good luck.

Closed plug gap and swapped coils for OEM for testing, same results. I'll check the voltage to the coil, but I am starting to lean towards fueling issue as these tests are during closed loop + wideband running lean af during it. I'll see if I can get a wideband log during the window to confirm.
 

serfma

New Member
May 1, 2020
5
0
1
27
Kentucky
1651082297799.png


Tested using a uScope on Injector 1, 4, 5, 6, 7, 8. During window of cut outs I have no change in the output from PCM. 2 and 3 are very hard to reach so I won't be able to test the last 2 for a bit. I have another Walbro fuel pump that I might just swap out to see if I get any improvements or changes. If I potentially lack a few psi of pressure due to gunk getting into the motor and damaging it, I want to know for certain.

Installed new motorcraft coils, going to test the power to each coilpack as well during the RPM band. Going to re-test the 12v power to the fuel pump right before it enters the pump so I know for a fact the pump is pulling enough power, and exactly how much amperage it's pulling.
 

serfma

New Member
May 1, 2020
5
0
1
27
Kentucky
So I have begun tearing down the engine. Taking off the lower intake manifold I noticed an absurd amount of oil pooling up everywhere on the driver side bank with a lot sitting inside recesses that oil shouldn't get access to without there being a problem with the gaskets. Brand new gaskets with less than 1k-2k miles. Did a leak down test and so far passenger side bank is over a 20% loss in leak down. Driver side going to be next. Hearing the leak out of the timing cover so I know it's rings. Looks like a rebuild is going to happen in the next week lol