Tuned EB Brief Misfires

Start with the new LPFS which seems to be the most logical giving your announced symptoms .

What exact oil are you running and at what speed and rpm are you driving at when you choose to pass another vehicle ? Could you think that you are starting a low speed pull ?
Are you going WOT while passing ?

You asked about oil before, Brian - it's not Valvoline, but it's high-grade synthetic 5w30 and has about 6K km's on it.

Every time but one, I've been driving at somewhere around 55 to 65 mph, and when the car does it's mighty cough (signaling the beginning of another "attack") it has occurred when I have made a sudden & dramatic demand for power. Perhaps not completely matting the pedal, but certainly very close. And FWIW, I have not downshifted each time. Probably once or twice, but definitely not every time. I can be certain because the last couple of occurrences were fairly recent.

ronemca said:

You asked about oil before, Brian - it's not Valvoline, but it's high-grade synthetic 5w30 and has about 6K km's on it.

Every time but one, I've been driving at somewhere around 55 to 65 mph, and when the car does it's mighty cough (signaling the beginning of another "attack") it has occurred when I have made a sudden & dramatic demand for power. Perhaps not completely matting the pedal, but certainly very close. And FWIW, I have not downshifted each time. Probably once or twice, but definitely not every time. I can be certain because the last couple of occurrences were fairly recent.

Click to expand...

Have you tried the low pressure fuel pressure sensor yet? (P/N 9F972)? I gave up and ordered one from the local stealership. It's supposed to be in tomorrow. parts.ford.com is showing these things on massive back order right now, so if you can get your hands on one, I'd suggest doing so. It's either paranoid ecoboost owners who read forums or there's something to rumors that this is a failure prone part ;) Original thread on the failure: https://www.mustang6g.com/forums/showthread.php?t=100140

Ford's own parts diagram: https://parts.ford.com/shop/en/us/fuel-injection-and-pumps/sensor-fuel-injector-pressure-7872979-1

I have one ready to go. And I’m quite comfortable & willing to change it...but I’d like to understand more clearly how it functions before I randomly swap what *could* be a perfectly good component.

A good friend suggested a similar swap of the Vacuum Purge Valve (atop the motor beneath the beauty shield) and I have one of those, too. But - like the LFPS - I’d prefer to gain a clearer understanding of *its* function too.

Thank you for offering your thoughts!

ronemca said:

I have one ready to go. And I’m quite comfortable & willing to change it...but I’d like to understand more clearly how it functions before I randomly swap what *could* be a perfectly good component.

A good friend suggested a similar swap of the Vacuum Purge Valve (atop the motor beneath the beauty shield) and I have one of those, too. But - like the LFPS - I’d prefer to gain a clearer understanding of *its* function too.

Thank you for offering your thoughts!

Click to expand...

The function is pretty simple: a loading cell within the part reports (via voltage or current) the pressure that it's experiencing inside the fuel rail. Unfortunately, the failure mode for this part seems to be to report a much higher pressure than the actual pressure, which causes the engine to run too lean...

I was one of those guys that replaced the LPFS as it did seemed to be a part that was failing, and at $30 off of ebay, and a 5 min job why not.

I think you need to get datalogs of these events and show them to your tuner.

Also the Check Valve should take care of the PCV valve, as if you have a CV, it will stop boost from the intake line going to the CC and then going to the PCV plate. Just make sure you get a proper CV that can handle the boost you are running, I have a 100psi UPR inline check valve.

I do have a UPR CV inserted on the hose...but right now the engine is wearing the PCV hose it was born with, and the CC and its hoses are in a box. I am now quite certain that the CC was not at fault for my earlier misadventures...and I intend to re-install it shortly. But before I do that - or tinker around with anything else (including the LPFS swap) - I am pursuing another couple lines of investigation.

I am grateful for the responses, and promise to report the results of my research/experimentation ASAP.

Well - today I had another "episode". I came straight home and changed the LPFS, re-booted the car and took a test drive. No improvement - the issue was exactly the same. I have been working off the same tank of premium fuel for several days (i.e.: no recent fill-up, no letting the tank run close to empty and no change of provider or grade of fuel) In fact, the tank is just a hair under half full, and therefore I'm still using the same fuel to which I added bottle #2 of injector cleaner.

However -- and this part is also exactly the same as always -- after the car was parked for awhile (in this case, 2 hours) it had healed itself; there were no performance issues on the way home from the theater...just like every other "episode".

WTF?!

Have you changed the LFPS and purge valve by any chance? My car had symptoms like some of the ones you're describing. Those parts solved all the problems pretty much. They failed at separate times and out of nowhere.
edit: they seem to inevitably fail btw, i see posts daily on the FB groups about someone changing parts after they throw codes or fail. Better to replace them early and save the headache

Well...since I have the new Purge Valve
sitting here I may as well change it. Hopefully it won’t be any worse.

A couple of questions:

1. Does outside air temp make any difference in when this occurs? Is it only during hot weather, or only during cold weather, or it doesn't matter?
2. When you fill up your fuel tank, do you stop after it clicks off, or do you top off the tank?

Engines need two things to run: fuel and spark. If the computer isn't reporting ignition problems then it must be a fueling issue. The pressurized fuel tank seems like a clue. In other cars I've owned the computer threw a CEL if there was a problem with tank pressure; I don't know if the same is true for our cars. If you top off the tank, say, in the morning when it's cool, then the car sits with a full tank as it warms up, the fuel expands. If you don't leave enough room in the tank for fuel expansion it can overflow into the vent system and saturate the charcoal canister filter in the vent line. Do that enough times and filter becomes blocked and the tank pressurizes. If I understand the way the system is plumbed, with the tank pressurized you can force fuel vapor under pressure through the EVAP purge valve, which can certainly affect mixture.

I'm not sure replacing your EVAP purge valve will fix this issue. If the charcoal canister filter is saturated and no longer venting the tank you'll have to have it replaced.

I am thinking of a fault with 1 or 2 of his ground wires is at fault and not giving a secure connection during the course of operation . He could have bad ground wires ..

Before I answer...let me first say thank you very much. Even if a solution is not discovered, the fact that you're thinking about this and posing thoughtful questions is greatly appreciated.

I would say it has been quite warm when I have my episodes. There have now been 6 or 7 - and they are usually (but not always) widely spaced apart from each other - but the first one was close to the start of this summer. And the last few have *definitely* hit when it's been really hot & humid.

I nearly always squeeze another cuppla bucks into the tank after the pump quits.

I went to install the Purge Valve that was sent to me by "block-otto" and it's the wrong part. They clearly show a CP758 as the right one, but it's not. So that was a bust. Evidently they don't even carry the correct part (FR3Z-9G297-C) but I've located it elsewhere. That said, just like with the swapping of the LPFS - which made no difference at all - I am even less keen to fork over another $35 for a part that may very well be A-okay.

FYI - at the moment the episode begins, the CEL begins flashing yellow, and continues flashing yellow for the whole time I'm fighting the problem. Once it has healed itself (which is usually after the car has been parked for a bit) the light goes out.

Sometimes I get a DTC (I'll have to look it up - I can't offhand remember what it is) It references the O2 sensor - which I presume is its reaction to the super-lean (or super-rich) exhaust gases it is smelling. I always clear the code, which does not fix the issue, but at least it clears the code.

Last-but-not-least...
If I had grounding issues I'd expect constant or more frequent problems. And most certainly I would not expect it to "heal itself" again & again & again during a 3-month period. And once it has healed itself, it's great again. It's more like...I dunno...excessive throttle (load) sucks up moisture or raw fuel or both...and/but a little down time lets it dry out or evaporate or drain or whatever...and it's okay again. Which reminds me - do any of us have the condensation-in-the-IC worry? It's pretty humid here lately.

ronemca said:

I would say it has been quite warm when I have my episodes. There have now been 6 or 7 - and they are usually (but not always) widely spaced apart from each other - but the first one was close to the start of this summer. And the last few have *definitely* hit when it's been really hot & humid.

I nearly always squeeze another cuppla bucks into the tank after the pump quits.

Click to expand...

When you top off your gas tank, especially in the morning before a hot day, you need to leave enough room in the tank for the gas to expand as it gets hotter. Take a look at this schematic:



The line coming out of the top of the fuel tank is the vent. It is connected to a charcoal canister that prevents the escape of fuel vapors into the atmosphere while allowing the pressure in the tank to remain equal to outside air pressure. The line running from the side of the charcoal canister is connected to the EVAP purge valve. After your car is warmed up and running the purge valve opens and allows the vapors trapped in the charcoal canister to be burned off in the engine. The valve opens and closes at the command of the computer.

If your tank is full enough, expanding fuel has only one place to go: through the vent line and into the charcoal canister. If the charcoal becomes saturated with fuel it no longer allows pressure in the tank to equalize with outside air pressure. This is why you shouldn't top off your tank. When the pump shutoff valve clicks the first time stop adding gas. If you want to be sure your tank is as full as possible without overfilling then just use a slower flow at the end, but stop after the first click.

I believe what's happening is your fuel tank is no longer properly venting because the charcoal canister is no longer functioning as intended. When it gets hot your fuel tank becomes pressurized, and that's why you heard a burp when you pushed open the filler flap. You need to let air out as the tank pressure goes up (like when the fuel gets warm and expands) and you need to let air in as you burn fuel to prevent creating a vacuum.

ronemca said:

I went to install the Purge Valve that was sent to me by "block-otto" and it's the wrong part. They clearly show a CP758 as the right one, but it's not. So that was a bust. Evidently they don't even carry the correct part (FR3Z-9G297-C) but I've located it elsewhere. That said, just like with the swapping of the LPFS - which made no difference at all - I am even less keen to fork over another $35 for a part that may very well be A-okay.

Click to expand...

This link (where I got the pic from above) has instructions to test the purge valve. For what it's worth, I agree with you that there's probably nothing wrong with it.

ronemca said:

FYI - at the moment the episode begins, the CEL begins flashing yellow, and continues flashing yellow for the whole time I'm fighting the problem. Once it has healed itself (which is usually after the car has been parked for a bit) the light goes out.

Last-but-not-least...
If I had grounding issues I'd expect constant or more frequent problems. And most certainly I would not expect it to "heal itself" again & again & again during a 3-month period. And once it has healed itself, it's great again. It's more like...I dunno...excessive throttle (load) sucks up moisture or raw fuel or both...and/but a little down time lets it dry out or evaporate or drain or whatever...and it's okay again. Which reminds me - do any of us have the condensation-in-the-IC worry? It's pretty humid here lately.

Click to expand...

If your fuel tank is no longer venting properly it can become over- or under-pressurized. If your tank is over- or under-pressurized when the EVAP purge valve opens it can cause exactly the sort of problems you are having, and it could also explain why your car runs fine after you shut it off. When you turn the car off the EVAP purge valve closes, so tank pressure is no longer an issue.