2016 Ford Flex Limited, AWD w/Ecoboost 3.5, just about 130,000 miles. Maintenance schedule upheld since I got the car, at about 75k miles I believe, including new OEM plugs at 100k.

Last week, while driving to work and entering the freeway, I experienced a hard misfire. Typical symptoms, loss of power, heavy vibration, flashing CEL. After maybe 30 seconds the flashing CEL went away and the car resumed running normally. I assume the computer shut down that cylinder when it detected the misfire to protect that cat. I tossed my cheap-o OBD reader in and found a pending P0306, misfire in #6. No other codes or pending codes pulled at that time. At work I just unplugged and re-seated the coil connector, cause that's all I could do with no tools. On my way home I was able to recreate the misfire again when entering the freeway.

First steps: Once home I pulled the coil and plug for #6 and did a quick inspection, all seemed normal. I then moved them, placing the coil in cylinder 4 and the plug in cylinder 5. My hope was the misfire would move to 5 as I happened to have a brand new NGK coil on hand I bought when Advanced Auto closed up shop in January.

The next day on my way to work I again goosed it getting on the freeway and recreated a misfire. Unfortunately, per the code it stayed in cylinder 6. Doh.

I then hooked up my laptop with Forscan and confirmed cylinder 6 is the only one missing (per mode 6 data). AI suggested using Forscan to run a injector relative flow test... ai lied, I don't have access to that on Forscan, it seems. I looked at fuel trims, shorts are pretty synced up, long is about 4-5% higher on bank 2.

AI said to look at fuel rail pressure to rule out a problem with the high-pressure fuel pump, so I did. Desired and actual pressures match, so the pump appears to be ok.

So, that is where I am at, mostly. I've read about possible condensation in the intercooler causing misfires, though it seems a little dubious to me that it would reliably occur always in 6. Maybe?

It seems more likely a failing injector, no? Perhaps The intake has been off recently, maybe 2 months ago, when the water pump and timing components were changed out, so it is possible a connector/wiring/seal got damaged in the process.

As the injectors are very hard to get to, what is my best next step? I was thinking of at least trying a high-quality appropriate fuel system cleaner... if the injector is partially clogged maybe it would help? Redline SI-1 is what I was thinking.

I’m not a mechanic but my first step on anything like that is to run some Lucas injector cleaner through it. I do that periodically as preventative maintenance.

Absolutely sounds like a failing direct injector.
Ugh, they're BURIED under the intake manifold.
And there is a coolant tube that runs under the intake that has to come out too.

Not an impossible job just involved.

Your getting into advanced diagnostics here, which is what I did for a living for many years.
That being said, it is very difficult to do online without out seeing the vehicle.
I would check what the fuel trims are when the code set in freeze frame.
Normally, but not always, misfire under load is ignition.
I would use a borescope and take a look inside the cylinder and back of the valves.

quote:

Originally posted by Krazeehorse:
I’m not a mechanic but my first step on anything like that is to run some Lucas injector cleaner through it. I do that periodically as preventative maintenance.

I prefer Red Line SI-1 Complete Fuel System Cleaner. It has THE Highest Level of PEA (< 34.5%) of any similar product, and does an outstanding job of removing the Carbon deposits that are common in GDI (Direct Injection) Engines. In this respect, it is superior to everything else on the market!

https://www.amazon.com/Red-Lin...r/dp/B000CPI5Z0?th=1

quote:

Originally posted by ScreamingCockatoo:
Absolutely sounds like a failing direct injector.
Ugh, they're BURIED under the intake manifold.
And there is a coolant tube that runs under the intake that has to come out too.

Not an impossible job just involved.

Yea, I'd love it if the injectors were more accessible... they aren't expensive but it looks like a pain to get too, and I haven't yet found a good video of them being accessed in a Flex... most videos of this engine are in the F150 and there are some differences. Heck, all the intake manifolds on the 150's are plastic, according to the videos I've seen, and the one in my Flex is not plastic. I'm not sure I'm up to the job, frankly. I don't like starting jobs I'm not sure I have the skills or tools to complete.

quote:

Originally posted by rizzle:
Your getting into advanced diagnostics here, which is what I did for a living for many years.
That being said, it is very difficult to do online without out seeing the vehicle.
I would check what the fuel trims are when the code set in freeze frame.
Normally, but not always, misfire under load is ignition.
I would use a borescope and take a look inside the cylinder and back of the valves.

I had Forscan running at one point when I recreated the misfire and I had the fuel trim PIDs active. I should have that data here, hold up..... here it is.

short term bank 1: 0%
short term bank 2: 0%
long term bank 1: 8.59%
long term bank 2: 11.72%

I've looked at the fuel trims multiple times over the last 4 days... the short terms seem to track pretty consistently with each other, the long term on bank 2 consistently runs 4-5% higher than bank 1. I think I've seen it as high as 15%, if I recall correctly.

Further context on when the misfire is replicable... I can reliably get it to happen when I punch the accelerator when I am already traveling at a high speed, such as cruising on the freeway then getting on the accelerator. That will reliably trigger a misfire in 6. What will not trigger is standing on the accelerator from a stop light. It will stay smooth there. AI seems to think that points to the condensation issue, and I am curious how useful AI will end up being, though I remain dubious on the intercooler condensation theory.

I can send my borescope into the plug hole pretty easily but I don't think I can get it to the backside of the valves without pulling the intake, right? I've never pulled an intake before.... It doesn't look too terrible... maybe I can manage?

quote:

Originally posted by nhracecraft:

quote:

Originally posted by Krazeehorse:
I’m not a mechanic but my first step on anything like that is to run some Lucas injector cleaner through it. I do that periodically as preventative maintenance.

I prefer Red Line SI-1 Complete Fuel System Cleaner. It has THE Highest Level of PEA (< 34.5%) of any similar product, and does an outstanding job of removing the Carbon deposits that are common in GDI (Direct Injection) Engines. In this respect, it is superior to everything else on the market!

https://www.amazon.com/Red-Lin...r/dp/B000CPI5Z0?th=1

I've got a bottle of that at home waiting for my gas level to drop in the tank...

My 2013 Taurus SHO exibited all the symptoms you've described just this past August. I have about 140k on the odometer. Turned out to be a fuel injector locking open and flooding the cylinder.

quote:

Originally posted by rizzle:
Your getting into advanced diagnostics here, which is what I did for a living for many years.
That being said, it is very difficult to do online without out seeing the vehicle.
I would check what the fuel trims are when the code set in freeze frame.
Normally, but not always, misfire under load is ignition.
I would use a borescope and take a look inside the cylinder and back of the valves.

I had Forscan running at one point when I recreated the misfire and I had the fuel trim PIDs active. I should have that data here, hold up..... here it is.

short term bank 1: 0%
short term bank 2: 0%
long term bank 1: 8.59%
long term bank 2: 11.72%

I've looked at the fuel trims multiple times over the last 4 days... the short terms seem to track pretty consistently with each other, the long term on bank 2 consistently runs 4-5% higher than bank 1. I think I've seen it as high as 15%, if I recall correctly.

Further context on when the misfire is replicable... I can reliably get it to happen when I punch the accelerator when I am already traveling at a high speed, such as cruising on the freeway then getting on the accelerator. That will reliably trigger a misfire in 6. What will not trigger is standing on the accelerator from a stop light. It will stay smooth there. AI seems to think that points to the condensation issue, and I am curious how useful AI will end up being, though I remain dubious on the intercooler condensation theory.

I can send my borescope into the plug hole pretty easily but I don't think I can get it to the backside of the valves without pulling the intake, right? I've never pulled an intake before.... It doesn't look too terrible... maybe I can manage?[/QUOTE


It's running lean on both banks, could be from a drop in rail pressure due to a bad injector, or pump, don't rule out a partially plugged catalytic converter.

Most borescopes have a mirror attachement that will let you see up, may have to turn the engine over a little to open the valve.
I would be making sure it doesn't have a loose seat.
Check fuel pressure when misfire exists., If it's out of range, time to dig into injectors, pump, or regulator.

In a diagnostic world, you get one hour, if it takes 15 minutes you will make good money on that .

Does it misfire if you power brake it?

quote:

Originally posted by Orguss:
My 2013 Taurus SHO exibited all the symptoms you've described just this past August. I have about 140k on the odometer. Turned out to be a fuel injector locking open and flooding the cylinder.

Pay attention to THIS...If the Injector is failing, this scenario can be catastrophic to the engine as cylinder washing can occur, where all lubrication is 'washed' away, and scoring of the cylinder walls can be the result! Worse that that, it 'may' even be possible for 'hydraulic lock' to occur in that cylinder if the injector fails open, potentially bending a connecting rod for the affected cylinder!

How does it do on hardest acceleration? You said you were getting on the freeway.

What happens if you floor it (and I mean floor it) at highway speed especially uphill? It can rather spectacular if they all freak at once under load. If they are original coils at that mileage, I'd replace 'em.

Your plugs are new enough, I'd clean and re-seat them while doing coils.

It has amazed me how they can do ok even when weak...and nary a code except a condition code like a misfire.

quote:

Originally posted by Orguss:
My 2013 Taurus SHO exibited all the symptoms you've described just this past August. I have about 140k on the odometer. Turned out to be a fuel injector locking open and flooding the cylinder.

This required a new injector, no?

quote:

Originally posted by rizzle:

It's running lean on both banks, could be from a drop in rail pressure due to a bad injector, or pump, don't rule out a partially plugged catalytic converter.

Most borescopes have a mirror attachement that will let you see up, may have to turn the engine over a little to open the valve.
I would be making sure it doesn't have a loose seat.
Check fuel pressure when misfire exists., If it's out of range, time to dig into injectors, pump, or regulator.

In a diagnostic world, you get one hour, if it takes 15 minutes you will make good money on that .

Does it misfire if you power brake it?

I have fuel rail pressures at time of misfire...
Desired: 14460 kPa
Actual: 14210 kPa

EDIT:
I actually have a poor quality picture of the graphs generated by Forscan for a moment of misfire that includes the fuel trims and the rail fuel pressure. If you look at the graphs themselves, in the briefest of moments right before the misfire was recorded there is a slight drop in actual fuel pressure. I can't pull the exact value, but if the above quoted Actual is 1.73% below Desired, then I'd say the brief dip is about 3, 3.3% before it comes back up to the captured pressure at time of misfire. Is that small dip enough to cause the misfire?

Here is the poor quality picture.

END EDIT

I don't have knowledge of specs, but these figures seem pretty close.

I only tried the power brake revving once and it did not misfire. I was in my driveway facing my garage door so I didn't try super hard, but it did not misfire. I'll try again here in a little bit. It is parked in a better manner for such tests.

quote:

Originally posted by 83v45magna:
How does it do on hardest acceleration? You said you were getting on the freeway.

What happens if you floor it (and I mean floor it) at highway speed especially uphill? It can rather spectacular if they all freak at once under load. If they are original coils at that mileage, I'd replace 'em.

Your plugs are new enough, I'd clean and re-seat them while doing coils.

It has amazed me how they can do ok even when weak...and nary a code except a condition code like a misfire.

Flooring it while already at freeway speeds reliably triggers a hard misfire on #6 only, kicking on the flashing CEL and resulting in running rough and limited power for maybe 30 seconds.

It doesn't appear to be coils or plugs since the misfire stayed with 6 after I moved the coil and plug to other cylinders (4 & 5)

They are probably right about the injector. And access probably mandates a valve back cleaning on a DI engine.

I'd budget for some coils down the line some then since there isn't an advantage to doing them with an injector.

Given per your description that this hard misfire occurred "suddenly" you have the code for it, you swapped coil and plug and the issue stays with original cylinder.

I would agree that it is an injector issue. And any fuel delivery tests are only going to confirm that.

If it were a situation where it had any light misfiring, of was a problem that came on and worsened, then injector cleaning product might be worth a try.

In this case, I would be pulling injector (or swap two and test).

As stated, running it for the time for injector cleaner to work is not good if you are driving it under all normal conditions with a bad injector if it is hanging and the computer fails to cut fuel.

If it cuts fuel, it may not "self clean" for quite a long time operating.

You may be in need of proper valve/intake plenum/runners cleaning. 130k is a lot of miles and not knowing if it was mostly highway driving, or worse, lost of short trips and stop and go.

Putting on a Catch Can, is a few hundred well spent dollars.

Mishimoto makes one that handles both the PCV and crankcase vent.

Chevron/Texico fuel with Techron, or use the additive.

quote:

Originally posted by sigmonkey:
Given per your description that this hard misfire occurred "suddenly" you have the code for it, you swapped coil and plug and the issue stays with original cylinder.

I would agree that it is an injector issue. And any fuel delivery tests are only going to confirm that.

If it were a situation where it had any light misfiring, of was a problem that came on and worsened, then injector cleaning product might be worth a try.

In this case, I would be pulling injector (or swap two and test).

As stated, running it for the time for injector cleaner to work is not good if you are driving it under all normal conditions with a bad injector if it is hanging and the computer fails to cut fuel.

If it cuts fuel, it may not "self clean" for quite a long time operating.

You may be in need of proper valve/intake plenum/runners cleaning. 130k is a lot of miles and not knowing if it was mostly highway driving, or worse, lost of short trips and stop and go.

Putting on a Catch Can, is a few hundred well spent dollars.

Mishimoto makes one that handles both the PCV and crankcase vent.

Chevron/Texico fuel with Techron, or use the additive.

So, this begs the question... how hard of a job is this? I've never done injectors of any sort. If I can manage, I'd like to do it myself, both to save money but also to learn and try to be more self-sufficient. Changing plugs/coils are easy.... how much past that is this job? Does it require special tools? Wish I could find a video, I'll have to do more looking.

Is it worth taking it to an actual mechanic with a better grade scan tool? Can they confirm bad/failing injector with a better grade of scanner? Is there a chance this is related to the water pump job? I had that work done by a pro, but he isn't the pro I would typically go to for diagnostics. But if it is potentially related, perhaps the situation properly calls for a return visit to him.

Can you bench test an injector?

Drop in fuel pressure when misfire, time to go after #6 injector, as mentioned, excessive carbon clean if visible on disassembly.

if im not mistaken.. you can access the injector harness for both side.. 2 differant ones and if you can get a wiring diagram you can ohm test the injectors and compare readings

quote:

Originally posted by thumperfbc:

quote:

Originally posted by Orguss:
My 2013 Taurus SHO exibited all the symptoms you've described just this past August. I have about 140k on the odometer. Turned out to be a fuel injector locking open and flooding the cylinder.

This required a new injector, no?

Yes, it required a new injector, which cost $220 for the part from a dealership.

Also, to sigmonkey's last point, I've only ever used Chevron 91 octane in the Taurus.