Focus ST understanding misfire and steps to take on fixing the issue.

Here are some simple steps to
Take to understand and figure out why your focus st might be misfiring. Some things I didn’t mention include improper gap on your spark plugs, electrical issue with the wiring harness leading to the coil packs, and bad gasoline. I am not a professional nor am sponsored or endorsed by any of the products shown. This is for educational purposes. I hope this helps in some way.

[@Sonicaceman]

Some of these vehicles have gremlins and the misfires is one of them. For those of you that have done a plug swap or replaced a coil pack and it fixed the problems you’re fortunate, no all misfire issues are that easy and a lot of people have dumped these cars because they have never figured out the issue, Ford doesn’t even know what causes it on some of the ST’s. There are a lot of variables to consider and a lot of sensors and grounds and carbon build up in some cases. I’ve been trying to figure my ST out and when I think I’ve got it the cel light comes back on for no reason with no warning. I’ve replaced plugs, all coils, the purge valve and I’ve cleaned my valves as well. The car will run perfect for hundreds or thousands of miles with no issues then one day if will start backfiring and running crappy and boom, cylinder misfires on one then multiple then cold start misfire or random misfire. The car really is my favorite vehicle and some have no issues like my brothers with over 100 thousand miles and never a cel light. My last ST had almost 47 thousand with 0 issues but I got greedy because it was a base mode ST1. My point is some of these issues are wear related and just a simple failure but a few of these like my vehicle just keep coming back for no apparent reason and they are very tough to figure out if you ever do. Thanks for the video and good luck to anyone dealing with these issues. I’m at just under 30 thousand and have had several cel lights and have replaced multiple components to no avail and have had the issue stock and tuned. Just be prepared for it if you love the car like me I plan on keeping it and dealing with it and hoping that I find a solution

[@TheAnderson-px9kk]

Had the same random misfire on mine found that the high pressure fuel pump had a glitchy sensor probably from the start & the pump eventually failed completely. After replacing the pump no more issues

[@Sonicaceman]

@@TheAnderson-px9kk Glad you were able to figure it out It’s been better since I’ve done some work and replaced a lot of failure items like O2 sensors, purge valve, coils and plugs. It wouldn’t surprise me if the hpfp is the issue and it’s intermittent because I still feel the shuddering randomly, especially when it’s cold Something to look into because I’ve replaced all the other items that would cause misfires

[@TheAnderson-px9kk]

@@Sonicaceman If you have connections that can help you with a spare pump to test that would help my tuner did this before we bought the pump because they are pretty expensive unless you go with aftermarket which I would not do especially if the car is tuned.

[@Sonicaceman]

@@TheAnderson-px9kk That’s a good idea. I’m not 100% sure I’m keeping car and I’m waiting for light to come back on. It hasn’t since I’ve replaced all the stuff but I’m still not convinced so if I keep it may I can convince my bro who has the same car to swap it and see if it fixes it. Waiting for the light to come back first Hope it doesn’t but I swear it was going to come on a couple times when it’s shaking and shuddering and stumbling when cold Thanks for the tip 👍🏻

[@wegiel1987]

I really hope you found the solution cuz I'm in the same state as you. If you can please share the solution thx.

[@dham99]

TLDR? Move one part around at first...dont do too many things at once. A specific cylinder misfire is fairly easy to troubleshoot at first... if you suspect plugs, swap plugs and drive around, see if the misfire follows the plug. Same with coil packs. On a engine swapped, supercharged Cavalier i had, a misfire was eluding me for months. Turned out I had wrenched on it so much, removing the coils/plugs/etc so many times i somehow tore/freyed the wire inside the clip to the injector. The exterior of the wiring loom as solid..but when i bent the wire to the connector (that clips to the injector), it bent like a folded piece of paper. I opened it up, sure enough was cut in half. I soldered it, and it was golden. My 2016 FoST was at the track this weekend and after literally JUST hitting 70,000 miles, I started getting major misfires under load. Cost me a whole day of racing. Checked plugs, gaps, check coils, nothing seemed off. Then ran my codes on the COBB AP and its showing P0088/P0087/P0192/P0300/P0301. So I either have a failing fuel pump or a bad sensor. The sucky part is it can be any one or combo of issues. Its a major PITA trying to troubleshoot misfires but you just have to start doing it piece by piece, generally looking at any most recent 'variables' that have changed. For me, being on E30, i started looking at fuel quality. So I'm going to be running it to E and running 93 to see if the problem persists. Then I may toss in the high side (i believe it is) fuel sensor on the front of the manifold (between the intake manifold and radiator). Its a good video to help guide people, the scope is prob the best advice here. But its important to try to 'follow' the issue...if your code was P0304 for cylinder 4 specifically, swap coil packs ONLY at first. If it changes, the pack is bad. If not, it may be the plug. Swap the plug. Etc. Sucks i had this issue as i got all my stuff dialed in and was tearing up the track...then when I really wanted to get some good runs in my car decided "nope!"... at least I was able to get it home and now I can casually TS it while its safe at home and not at a track or 4 hours from home lol. Dont get discouraged and give up...its a nice feeling when you finally figure it out and are like "SOB...thats all it was?!" ^_^

[@johnlefever3220]

Misfires on these 2 liter motors are common, there isn’t anything wrong with them it’s just how they operate, just running to the store 5 minutes away I get 15 misfires sometimes 10, it’s nothing to worry about, it’s the knock and the negative ign corrections you want to watch out for

[@johnlefever3220]

I’m stage 3 with msd coil packs and one step colder plugs gapped to .26 as recommended by ngk and my tuner no matter what misfire is always going to happen most of the time under idle after cold start and if you have the crackles and pops tune

[@kirkgardner8485]

I’m misfiring but I don’t have Cobb, never throws a cel though, on the third set of plugs 70k miles on it now.

[@pulsartech2945]

Do you have a link to the scope? Good video just hate the orientation it was filmed in 😂 Im trying to track down my misfire on my '13 FoST. Get worse some days, does it warm or cold motor at idle. New plugs gapped @.031 on NGK 6509s 60k miles. No smoke once exhaust is hot enough to remove condensation. No DTC codes, no misfire data stored on the PCM 🤷🏼‍♂️ so I'm at a loss

[@barberhomieciscofreshcutz1276]

Pulsar Tech did you ever figure out the mis Fire problem? I’m getting cylinder 4 mis Fire , everything on the car is brand new I get misfire codes but nothing on the pcm I think it’s my injector even tho it’s only 5 months old

[@pulsartech2945]

BarberHomie CiscoFreshCutz I didn’t, I ended up selling the car back to the dealership 99% sure it was wiring harness related. They wouldn’t look at it even though I brought cash and the other option was guaranteed payment through warranty

[@alexandracasales421]

I have a misfire on cylinder 1 and 4 and Ford doesn’t know how to fix it, I changed all my coil packs and spark plugs and still nothing. Any advice? Just hit 100,000 miles

[@jaimehernandez4995]

Put in seafoam high mileage seemed to help best guest it’s fuel injector dirty and valves are too

[@JaySubi53]

What was the symptoms?

[@MichaelDouglas-24]

So you recommend doing coil packs huh? I'm gonna have to try this just to be safe

[@brunogois9854]

my car is failing when it gets to 15 psi, this starts after i changed the spark plugs! but do not set any light on the panel does anyone know what is going on?

[@xpire.3560]

So my accessport says cylinder 1 misfire I don’t think it’d be anything other than plugs and coil packs

[@Gxrrettx]

Did you get it resolved?? Mine is doing the same

[@peterAZ06]

@@Gxrrettx so are you changed the number 1 coil pack?

[@Gxrrettx]

@@peterAZ06 I did everything possible. Turns out cylinder 1 is completely dead.

[@DewaldN]

@@Gxrrettx How tf does 1 fix this ?

[@Fightmma12]

Fuel injection anyone