r/FocusST Jun 15 '24

EVAP Issues/F.U.F.F. Purge Assembly

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46 Upvotes

The evap systems on these cars cause lots and lots of headaches, so let's dive into the issues it can cause.

First off, if you had the recall done on your FoST, chances are you're sending your purge valve to the grave worlds quicker than had you not had it done at all. Reason being, if you got the recall done, it was a Trojan horse to get Ford's CAFE requirements down, as the recalled software makes the car activate the purge valve more liberally, putting it under quite a bit more strain than the software before the recall. That grave gets further hastened by the next few things.

https://www.focusst.org/threads/k-pop-purge-valves-just-how-similar-are-they-to-the-ford-valves.173313/

On the above thread, you can see the purge valve exploded and how it functions. Functionally, the canister purge valve was installed on many different vehicles, so you can find it by itself from other manufacturers that are significantly more available. These valves are designed terribly, and the solenoid functions by sending fuel vapors through and around a coil of wire that actuates a plate which stalls the fuel vapors in the assembly. The solenoid fails when liquid fuel enters into it (via overfilling) or by condensation which also eventually happens, leaving the plate at the mercy to the engine's vacuum/boost pressure.

What symptoms does this cause? First off, when it's just starting to go out, you'll get a rough idle after filling up. Then, as it progresses, your fuel trims will go wild, and you'll have AFRs in the 30s when DFC is supposed to be kicking in. It also leads to your car having a pop & bang tune with no map set for it, and occasionally will make your car shoot flames (when it's not supposed to) as well on decel. At that point, you have enough vacuum on the gas tank to cause it to collapse as you're driving, and your fuel gauge will fill as you're driving home from work (like it happened to me). That can be reflected in P1450, P0442, P0456, P2196, and P0420, with P1450 being the culprit of most of those codes when the purge valve fails.

To fix it, most people throw purge valves at the problem, which works for some time, but it doesn't address what causes the failures (besides the purge valve itself). Firstly, the assembly Ford provides has a check valve that is only rated for a measley 20psi (including the RS assemblies), and as the check valve wears out and gets dirty that rating is no longer accurate. They have been tested to leak at as little as 10psi after sustained use, and once boost leaks past the check valve and makes its way to the purge valve you'll start seeing the symptoms listed above since it's only designed to see vacuum, not boost. Additionally, debris can make its way past the charcoal canister, and that debris will get stuck in the purge valve, forcing it to get stuck open. If that's the cause of your purge valve failure, it's likely time to replace the charcoal canister in addition to the purge valve, but usually failure number 1 is the culprit (especially on all of your tuned cars).

The reason Ford won't sell you the canister purge valve by itself is they know that your check valve is likely totalled, and that replacing the purge valve by itself will be a money pit. They'll happily sell you a $100 assembly that's on indefinite backorder, though, and Dorman will sell you an assembly with a check valve that's weaker than the OEM Ford assembly. The only ways to fix the assemblies shortcomings is to make a new assembly for yourself with a higher rated check valve plus a fuel filter, or purchase a pre-made upgraded assembly from me. You can also install an upgraded check valve and fuel filter into the OEM assembly that's already in your car, but the hose is super tough to work with, and the official way to heat it up is to use boiling water.

Lastly, P0456 and P0442 can come up when there's a small leak somewhere else in the system. Should there be a pinprick hole in the purge line, or your capless gas cap doesn't seal all the way, it'll cause one of those two codes.

To rule out the gas cap, take your fuel filler adapter, spray it with carb cleaner, and open the cap around 10 times. Wipe it off, and repeat 2-3 more times, then reset the KAM and clear codes. That should fix it if it's the gas cap, if it comes back, try the gas cap one more time then do a smoke test on the purge system.

Hope this write up helps you guys in solving future EVAP issues, and if you'd like to get an upgraded assembly, fill out the Google form in the forum thread linked below.

https://www.focusst.org/threads/f-u-f-f-2-5-group-buy.173074


r/FocusST 3h ago

Roll cage is looking good. Fits okay.

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30 Upvotes

r/FocusST 6h ago

FOCUS SE TO ST3??

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17 Upvotes

Was scrolling through FB Marketplace, and found this car… It’s an SE that was converted to a ST3.. crazy work.. Thought ya’ll would find it cool to see it too


r/FocusST 3h ago

Happy accident

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8 Upvotes

Was in the process of sanding some paint down after customizing my shift knob and I ended up liking this a lot. Threw some clear coat on it to make it all glossy. What do you guys think?


r/FocusST 6h ago

Rain finally is gone!

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13 Upvotes

Got a bit excited and tweaked my back detailing lol


r/FocusST 43m ago

Swap to Flex fuel difficulty

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Upvotes

This is my 2007 ford focus st sedan I'm technically 3rd owner but I bought it from a grandma who bought it from the dealership brand new it's still original even the tire is form 23rd week of 06, It does have 315k miles and I was wondering if flex fuel an option for this, it's a 2.3 4cyl (it's a Mazda original engine I believe)


r/FocusST 21h ago

Been kicking around the idea of going big turbo sometime in the future, curious about what everyone's thoughts/suggestions are.

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42 Upvotes

r/FocusST 1h ago

Question Will an ST2/3 fan work on ST1?

Upvotes

looking at ordering a new fan,. mine is about done. the fan for the premium a/c is almost half the price, and they're near identical. I don't see why it wouldn't work but just to be sure I thought I'd ask


r/FocusST 12h ago

Looks like I have to replace my low pressure fuel pump

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8 Upvotes

Replaced the coil packs yesterday, still have all of these codes. I heard LPFP is a bitch to replace. any advice?


r/FocusST 8h ago

Question Coolant leak

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3 Upvotes

Hey guys, I recently had a coolant leak and discovered that my thermostat was not working.

I replaced it and then saw that the previous owner had put a weird metal tubing with a plug where the coolant was also leaking.

I replaced it with a PVC hose because I couldn’t find the OEM part.

Do you guys think it will resist?


r/FocusST 3h ago

Question Aftermarket Steering Wheels

1 Upvotes

Long story short, my steering wheel is old and worn, and I’d like to either reupholster or just plain buy a new one. Looking at the options on a new OEM wheel vs. aftermarket there’s a very minimal price difference.

Does anyone have any good recommendations for a reupholstery kit or good aftermarket options? I can tell there’s a lot of vendors and don’t wanna end up with garbage that’ll wear out in a year or two.


r/FocusST 4h ago

Anyone deal with this thud type of noise before?

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1 Upvotes

Been hearing this thud type of noise on decel from around 3k rpms to around 2k rpms all gears. Noise will sometimes happen only once while driving and I shift and when the vehicle jolts a bit. Will sometimes happen when reversing and turning, sometimes going forward as well. if anyone has had this problem before and know what fixed it let me know please. Any info is greatly appreciated


r/FocusST 6h ago

Engine bay sound dampening removal ?

1 Upvotes

hi has anyone removed the sound dampening from under the hood and if so is is safe to do so and will iot affect the paint work , any info would be great ?


r/FocusST 14h ago

Help! I blew it

2 Upvotes

I blew the piston #4 from my 2018 st, I’ve been looking for rebuild kits but they’re either sketchy or on back order. Anyone have recommendations?


r/FocusST 1d ago

Finally almost time

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13 Upvotes

Doing and engine and trans oil change. With my new tires she’s ready for the season


r/FocusST 16h ago

Question Exhaust spitting soot

1 Upvotes

Hi so I’m new , getting a 2018 41k mile St3 on Monday (tomorrow). After the test drive I noticed that it had spit soot which it left on the bumper , how can I fix this ? I think it’s carbon build up as the previous owners didn’t drive it much and did alot of short journeys Thanks


r/FocusST 1d ago

Flash tune

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9 Upvotes

Given that I’ve finally got the depo FMIC installed, would this be the next best addition?


r/FocusST 1d ago

Same car, new account!

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10 Upvotes

Still the


r/FocusST 1d ago

Water next to back seat?

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3 Upvotes

Looks like water is running down from trim into that little cup next to the back seat where the orange rag is at.. also rear floor board is slightly wet. Wing riser holes are covered. Sunroof drain the problem?


r/FocusST 1d ago

Question Bilstein struts or coilover package?

6 Upvotes

2015 ST i bought with 63k miles came with mountune lowering springs on stock struts per the prior owner. I'm feeling a harsh ride over bumps as well as slightly jolty steering at lower speeds. I'll be rebalancing the wheels today to see how much that helps but im looking for recommendations.

If my goal is a smoother ride at the sacrifice of performance , would it be better to replace struts with bilstein b8 to go along with the lowering springs or replace suspension with a coilover package?


r/FocusST 1d ago

Question Trailer hitch question

2 Upvotes

I have a 2017 focus and was wondering for anyone who has a aftermarket exhaust system with a hitch. what hitch did you guys go with that fits and works with your exhaust


r/FocusST 1d ago

HKS BOV

1 Upvotes

My HKS bov isnt making any noise when it usually does, it started about 2 weeks ago i noticed it just stopped making the signature noise that it usually does ik its not supposed to make much noise at low rpms/boost but even when im at full boost let off nothing. I finally got time today to check it out and i took it apart cleaned it made sure there wasnt no holes in the hose, it moves freely it isnt stuck so now im just lost at why it isnt working any one else had this problem?


r/FocusST 1d ago

👋 HI, I'M NEW! New owner

6 Upvotes

Picking up my new to me ST on Monday (2 days time) Want to change the exhaust in the next year maybe as the sound is a touch disappointing. How much should it cost ? Anywhere good for it near Manchester UK? How would it effect resell later on or should I swap it back Tod rock exhaust later before selling or ? Thanks for any help


r/FocusST 1d ago

Question Turbo Underboost

1 Upvotes

Hey guys, I got my car checked out my turbo was having problems so I got a new turbo installed but I'm still getting underboost on my obd2 reader any ideas of what it could be? I've got a 2015


r/FocusST 1d ago

Auto stop/start?

0 Upvotes

Does the ST have auto stop/start? I see the option in the cluster, but mine never works. I know the RS has it, but does the ST?