2019 Backfire issue?

[5280tunage]

Hey all, hoping some folks can come up with some good ideas here. Over the last 2 months or so, this issue has crept up virtually every time I fill up. It ONLY happens when I fill up and it happens within one or two minutes after filling up, and within less than a mile of driving. So for those of you that may not know my mods, I have SPD turbo adapters, SPD downpipes, full custom exhaust, O2 spacers for the cats (I did not do the cat delete), CAI, Mishimoto intercooler, Plugs with less than 10K on them (the Ruthinium plugs, properly gapped), and a 5star 91 tune to match the upgrades.

So this has happened probably 80% of the time over the last 2 months or so, whenever I fill up, as I'm leaving the gas station, after light acceleration and letting off the throttle, I get a backfire. It literally feels/sounds like I drove over a plastic bottle each time and I can lightly feel it in the chassis. I'm running the exact same setup, exact same tune, that I've had for 2 years. Nothing else has changed. The only thing I can think of is that about 3 months or so ago, I ran a can of SeaFoam through the fuel system, but that's it. I don't like this and I'm concerned it may damage something major over time, any thoughts on what I could/should do, or what might be causing this. Again, I can't stress this enough, I can drive 200 miles with no issues, but if I fill up, and drive away, there's a good chance I will get a backfire, and only one, never more than one.

thanks in advance, oh, and absolutely no CEL's or warnings from the vehicle at all. No loss of power, no stuttering, just a crazy loud backfire.

And I did find this thread, but there really never was a resolution or outcome. https://www.expeditionforum.com/threads/engine-backfire.51994/

 

[SyndicateZ]

evap canister

Also dont overfill the tank ( stop pumping once it click)

 

[GlennSullivan]

Is it possible that there is an issue with the evap system that is related to what is going on? Is it absorbing too much fuel vapor during refueling process and sending it to the engine upon restart, which is causing the backfire?

I would go a step further than suggested above and try fueling to only 3/4 of a tank. If the problem goes away, check all evap system components, replacing as necessary and then slowly increase the fill level.

 

[GlennSullivan]

Is it possible that there is an issue with the evap system that is related to what is going on? Is it absorbing too much fuel vapor during refueling process and sending it to the engine upon restart, which is causing the backfire?

I would go a step further than suggested above and try fueling to only 3/4 of a tank. If the problem goes away, check all evap system components, replacing as necessary and then slowly increase the fill level.

The more I look into it, the more I think is is a bad EVAP purge valve, which, if working correctly, should slowly (over time and after warmup) release fuel vapors collected in the charcoal canister during refueling back to the engine to be burned. If malfunctioning or stuck open, it could, upon startup, immediately release all fuel vapors collected during refueling to be burned - backfire.

What I do not understand is why the vehicle is not throwing any codes.

 

[5280tunage]

I agree @GlennSullivan , I would think any sort of fuel system issue would be throwing codes but I haven't had a single CEL. The real trouble too is I can't even take it in to get something like this fixed under warranty without codes, telling the dealer service teams that I'm getting a backfire, and only when filling will be pretty hard to replicate and I'm sure they won't do anything without the codes.

I typically always stop filling when the pump stops, but I will pay attention to that more.

From the looks of it, the evap canister on these is close to $300 so I would definitely want that done under warranty if it truly needs it. Also means I need to basically remove my tune, since that clears any codes, which I don't want to happen if it actually does throw a code.

 

[99WhiteC5Coupe]

When an evaporative system solenoid fails - two things can happen.

If it sticks “open” - it will allow excess fuel vapors into the intake at startup, usually resulting is a rough idle or engine stall. It is possible to cause an engine backfire.

If it sticks “shut” - it will not allow excess fuel vapors into the intake when designed, and eventually “load-up” the charcoal canister, ruining it.

 

[5280tunage]

so from what i can tell, there are two solenoids, a purge and a vent. The purge looks to be on backorder, while the vent seems to be available, and is roughly $30, I'd be open to replacing that if the job isn't too hard, I have no idea where that is to be honest.

I would still think that if a solenoid was stuck open or closed, it would fire off a CEL wouldn't it?

 

[GlennSullivan]

I agree @GlennSullivan , I would think any sort of fuel system issue would be throwing codes but I haven't had a single CEL. The real trouble too is I can't even take it in to get something like this fixed under warranty without codes, telling the dealer service teams that I'm getting a backfire, and only when filling will be pretty hard to replicate and I'm sure they won't do anything without the codes.

I typically always stop filling when the pump stops, but I will pay attention to that more.

From the looks of it, the evap canister on these is close to $300 so I would definitely want that done under warranty if it truly needs it. Also means I need to basically remove my tune, since that clears any codes, which I don't want to happen if it actually does throw a code.

I'm certainly confused why you are not getting any CELs. If for no other reason the backfires should be picked up by the knock or misfire sensors and should set a CEL as detonation or misfire.

99WhiteC5Coupe mentions 2 possible scenarios, copied below. I would thing that #1 is certainly a possibility, It can be stuck open and for some reason the ECU can't sense the fault or the tune is preventing the ECU from setting the code.

I would also suggest a third possibility, which is according to "normal system operation" after fueling the valve is not supposed to open until the vehicle comes up to temp and then only to gradually feed vapors back into the combustion cycle. Is it possible that you tune could be inadvertently causing some misfunction to the valve / system where it is opening the valve right after restart?

If it sticks “open” - it will allow excess fuel vapors into the intake at startup, usually resulting is a rough idle or engine stall. It is possible to cause an engine backfire.

If it sticks “shut” - it will not allow excess fuel vapors into the intake when designed, and eventually “load-up” the charcoal canister, ruining it.

Also
With the Mods that you have described, I would suspect that the Dealer and / or Ford will blame whatever is happening as caused by the mods and not cover any of this under warranty.

 

[5280tunage]

@GlennSullivan Couple things, I will remove the tune and see what happens next fill up. But again, I've been running the tunes and mods for years and this is just now starting to happen. Which solenoid are we talking about, as I see two possible evap solenoids.

And I hear you on the mods and warranty, but I'll fight that, I haven't done anything to fuel system, I don't see how a cat back exhaust, ypipes, or adapters could possibly impact the fuel system in a way to create a backfire.

 

[GlennSullivan]

@GlennSullivan Couple things, I will remove the tune and see what happens next fill up. But again, I've been running the tunes and mods for years and this is just now starting to happen. Which solenoid are we talking about, as I see two possible evap solenoids.

And I hear you on the mods and warranty, but I'll fight that, I haven't done anything to fuel system, I don't see how a cat back exhaust, ypipes, or adapters could possibly impact the fuel system in a way to create a backfire.

I think putting stock tune back in may tell us some things at least with CELs

Everything I see says it is a failed Purge Valve which controls the vapor movement from the collection canister at the fuel tank to the intake. It would make sense that this was working all along and has just failed and that is the reason the backfiring just started happening.

This is also evidently a very common part failure after Ford changed the design in the early 2010's. Again what is strange is that in all cases there are multiple codes thrown when this happens, so something is keeping your ECU from either knowing about the failure or reporting on the codes.

The Purge valve is located somewhere under the hood near the intake (I don't have a Gen 4 so can't tell you where). The Charcoal Canister is located adjacent to the fuel tank and the canister vent solenoid is attached to the canister. But I would focus on the purge valve/

Here is a video that shows how to test the valve, it is for an older car but evidently the valve has not changed. https://www.youtube.com/watch?v=S6dsQoq73aE

You are preaching to the choir about the warranty denials, I'm just reiterating what I'm seeing with other people in the same situation and Ford is the worst out of any of them on denials. They have hosed me on some stuff that should clearly have been covered and my truck is bone stock.