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Cylinder 4 misfires.

29K views 53 replies 9 participants last post by  TheBlueMistress17  
#1 ·
Hello everyone. Long time lurker first time posting. I have a 2018 Ecoboost with the following mods. K&n intake, CVF race Inter cooler, MBRP catless downpipe, y pipe and tuned with tune plus.
About a week ago I turned on my car and it’s started right up but the exhaust was definitely sputtering until the car warmed up. It threw the cylinder 4 misfires code along with the code for Misfire at startup. I drove it a bit and it drove fine. Turned it on again later and it started as regular.
I swapped my 4 cylinder spark plug with the 1 and still threw that code the next day. Now this issue is not throwing me the code every time and regular starts are more common than the sputtering ones.
I live in Miami so plenty of shady garages here and I am out of warranty due to miles. The one shop I did find doesn’t have an opening till 2 weeks. Any one have any suggestions? I highly doubt it’s a head gasket issue since I see no milky oil, no smoke from the back only regular morning smoke and no knocks. I must add that on the CobbAP I have the gauge for misfires and most of the times it doesn’t go over 10. One time on a start I did see 45. It’s very inconsistent. Any input would be highly appreciated.
 
#8 ·
Hello everyone. Long time lurker first time posting. I have a 2018 Ecoboost with the following mods. K&n intake, CVF race Inter cooler, MBRP catless downpipe, y pipe and tuned with tune plus.
About a week ago I turned on my car and it’s started right up but the exhaust was definitely sputtering until the car warmed up. It threw the cylinder 4 misfires code along with the code for Misfire at startup. I drove it a bit and it drove fine. Turned it on again later and it started as regular.
I swapped my 4 cylinder spark plug with the 1 and still threw that code the next day. Now this issue is not throwing me the code every time and regular starts are more common than the sputtering ones.
I live in Miami so plenty of shady garages here and I am out of warranty due to miles. The one shop I did find doesn’t have an opening till 2 weeks. Any one have any suggestions? I highly doubt it’s a head gasket issue since I see no milky oil, no smoke from the back only regular morning smoke and no knocks. I must add that on the CobbAP I have the gauge for misfires and most of the times it doesn’t go over 10. One time on a start I did see 45. It’s very inconsistent. Any input would be highly appreciated.
Im in Miami also. Does your AC automatically start up when you start the car? If so, try to make sure the AC is off, and see if the problem may curtail a bit.
 
#21 ·
Yes I have a MBRP Catless. yes i Checked the gap and tonight I even changed out the 4 plug with a brand new one. It started well with no misfires on the AP but I will see tomorrow morning. The plugs have been used for no more the 2k miles. Yeah the misfire is only on cylinder 4 according to the AP and about 2 weeks ago it began.
 
#22 ·
Good morning. The plugs should be fine, then. You earlier indicated that your reservoir tank was "lowering as usual" or similar to that wording without me going back and checking. In all honesty, the coolant system is a closed loop, and evaporation should have no effect on it. If you're missing any coolant after a some time, it may be possible that you have a small fissure in the gasket around cylinder 4. That might also be a good explanation on why it only happens on morning cold starts, when your engine is a stiff as possible, but then goes away after some combustion warms it up some, and allows the head to rest better in place. I don't wanna alarm you, as this is only conjecture, but you may wanna do a compression test if you're able.

If your coolant is absolutely NOT lowering, then yeeeesh, I'm not sure. The only thing really left would be to try swapping the coils from one cylinder to another and seeing if the 'misfire' follows it.

More specifically to the previous question, was there any change made to the car two weeks ago, when this began? AP install? A new tune?
 
#25 ·
yeah adam had me change those two out. Unfortunately I am just over 60k im at 61K. I will actually be doing a compression test this weekend and ill see how that turns out. I have an appt with SS Performance on the 21st so they can take a look at it but I just want to hit everything before they try and redo everything that I coudlve tried. With the car being tuned and FBO I tried looking up places that seemed like the could handle that and these guys seem to be the only ones that seem reputable. I just find it really weird that I am having no symptoms of a blown gasket and the car being able to idle just fine. I decided to give the car a break today so tomorrow I will take it out for a spin with the brnd new spark plug in the 4 cylinder and see how that goes.
 
#27 ·
I get my plugs from tune plus and they are pre gapped.
I actually replaced the 4 cylinder with a new one last night and just about an hour ago I started the car and it started just fine to stuttering or anything. But then I got two new codes. One for cylinder 2 and I forgot the code number but it’s for random misfire. Along with the 4 cylinder misfire and the misfire on first 1000. Only god knows what’s wrong with my car now lol
 
#54 ·
That's super ironic in my case, as I just replaced my ngk 6510's that went over 40k+ miles/ lasted almost two years, keep in mind tho I only have airraid CAI and MSD coil packs and basically a stage 0 tune from lundracing. My father has me convinced that I didn't need a step colder plug (even tho I was told that's recommended but it's entirely up to me and the car should be fine) and I went from a .028 gap to replacing them with OEM Ford motorcraft plugs that were at .032. as of today(9-21-2021) I started getting a random misfire code P0136 and my dad doesn't really know much about my motor/ the newer engines compared to pushrod,but when I initially switched to NGK when I got tuned I never had this issue(back when I was at 30k miles but now I'm at 75k, bought the car in late 2018 with 23k) also keep in mind while back when I didn't know much I let my garage mechanic for an old company I work for cut off my mufflers for cheap and all he did was tac in 3 inch equal length pipe (but it's not clean and you can tell he didn't put time into it) my pops thinks it could be a possible exhaust leak, on top of when my car backfires on WOT(not all the time tho, only under rapid acceleration and quick gear changes when timing starts to go +). We both did a some homework on it and we found that it could be a multitude of things since our motors naturally knock. That it could be 1:bad plugs 2: coil packs 3:O2 sensor.

But my question is,
Could the fact that I went from 1 step colder plugs that were pre-gapped to 0.028 to Oem's that were gapped at 0.033 be a factor in the cause? Or is there something I'm missing?
 
#28 ·
What spark plugs were you using, when this problem started, and what are you using now? Tune+ has changed plug manufacturers from time to time. Also, Tune+ sells gapped and ungapped plugs. Did you check the gap yourself? They should be .028". Always check them yourself. Just be careful, as the center electrode is fragil. Are you using the stock heat range plug or one colder? Does no. 4 spark plug look or smell any different than the other 3? It would be best to check the plugs right after a cold start event, when the misfire event occurs. Don't wait for it to stop misfiring. When you have misfire, shut it off right away, and pull the plug. Burning antifreeze has a very distinct smell that you may notice on the spark plug or at the exhaust exit. It's possible to have a damaged head gasket that leaks a small amount of coolant into the cylinder, when it cools down, and it burns out of the cylinder during cold start and warm up, then seals back up. Burning coolant would show as white smoke, with a sharp acrid odor. If it's a head gasket, it will get worse with time. Do you have a 93 octane or E-30 tune?
Carbon buildup on the intake valves is not common on our engine, even without a catch can, but the most common symptom of it is cold start and cold driveability. What oil do you use? A full synthetic, with an API rating of SN+ would be best. If you want to look at the valves, the intake manifold comes off pretty quick and easy. Tune+ made a YouTube video on how to remove it, in conjunction with installing a catch can.
Bad fuel injector spray pattern can also cause cold start misfires, if you wanted to swap that. I wouldn't think that would be a problem at 60k miles, unless you were using some crap gas. Do you use Top Tier gas?
Answer my questions, and keep us posted, please.
 
#31 ·
What spark plugs were you using, when this problem started, and what are you using now? Tune+ has changed plug manufacturers from time to time. Also, Tune+ sells gapped and ungapped plugs. Did you check the gap yourself? They should be .028". Always check them yourself. Just be careful, as the center electrode is fragil. Are you using the stock heat range plug or one colder? Does no. 4 spark plug look or smell any different than the other 3? It would be best to check the plugs right after a cold start event, when the misfire event occurs. Don't wait for it to stop misfiring. When you have misfire, shut it off right away, and pull the plug. Burning antifreeze has a very distinct smell that you may notice on the spark plug or at the exhaust exit. It's possible to have a damaged head gasket that leaks a small amount of coolant into the cylinder, when it cools down, and it burns out of the cylinder during cold start and warm up, then seals back up. Burning coolant would show as white smoke, with a sharp acrid odor. If it's a head gasket, it will get worse with time. Do you have a 93 octane or E-30 tune?
Carbon buildup on the intake valves is not common on our engine, even without a catch can, but the most common symptom of it is cold start and cold driveability. What oil do you use? A full synthetic, with an API rating of SN+ would be best. If you want to look at the valves, the intake manifold comes off pretty quick and easy. Tune+ made a YouTube video on how to remove it, in conjunction with installing a catch can.
Bad fuel injector spray pattern can also cause cold start misfires, if you wanted to swap that. I wouldn't think that would be a problem at 60k miles, unless you were using some crap gas. Do you use Top Tier gas?
Answer my questions, and keep us posted, please.
I am using the NGK plugs pre-gapped sold by Tune+. When I pulled the plug it was a little bit more worn and black than the others but not by too much to cause alarm. It did smell different more of a burnt smell. it does smoke on a cold start but nothing apart from the usual morning starts as you can see in the video above. i have it tuned for 93. My last oil change was with Pennzoil full syn. as far as gas my last fill up was with 93 from Chevron- but i did recently move and I had to put gas on a Raceway station and that is literally when it started happneing the next morning. I dont want to put too much though into the gas as ive never had a batch fill up before but ive ran with the new gas about 30 miles so far and it has only stuttered once. I just dont think it would be the gas but I cant knock it out. Tomorrow is my day off and I will be doing a compression test and ill post the results here.
Does anyone know what the pressure should be for the test? I read somewhere else it shoud be around 160-170. Just want to make sure.
 
#29 ·
My money is on the head gasket. The sputtering at startup is coolant in the cylinder. Let is sit for a day, pull the spark plug, get a flashlight and a stepladder, and climb up i top of the motor to look in. I’ll bet you see liquid. Tape a QTip to a straw or something to get a sample of the liquid to see what it is. I had identical symptoms (but only after skittle isle for 2 days) and mine came out orange...coolant.
 
#32 ·
I have done compression tests before but never on a push to start car. Is the process still the same. Obviously remove all boots and plugs but as far as cranking, Im guessing I just hold brake and push the button once till it times out? I saw one video of a GT350 owner removing some fuses but then read on other forums that it should be the same. Anyone done them before on push to start?
 
#35 ·
Do what I or RichBrew suggested, regarding the head gasket. Normally a compression test would be done with a warm engine, but in your case, since your issue is when the engine is cold, I would check it with a cold engine, and see if all 4 cylinders are about the same. Also, look in cylinder no. 4 for coolant, after you test it's compression.
Personally I wouldn't use a colder heat range spark plug, on a 93 octane tune, unless I was road racing the car, or the plugs didn't look good. You could try putting the stock heat range motorcraft plug back in.
 
#36 ·
So I let the car sit a whole day and just now I removed the spark plug and didn’t see any coolant residue. Also when I did the cold start it started perfectly fine. That spark plug has been running for about 10-15 miles
 

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#37 ·
Hey man how’s it going? I had a similar problem as you and tried everything here to no avail. Then I decided to upgrade the head gasket and switch to arp head studs to see if that would help. Well, when we took off the head there was a deformation by cylinder 1 which is the cylinder I was getting the misfire on just like you with the number 4. Had to send it to a machine shop to fix it. I know that’s a big jump from the do it yourself quick fixes and a lot of money but it’s better than paying for a new engine. Good luck to you and I hope you figure things out brother.🤜🏼💯
 
#40 ·
Please let me know what the results were for you guys. I have a misfire in cylinder 4 and have the exact same symptoms,only on startup,no white smoke, I do seem to have noticed less coolant in my tank,maybe an inch under minimum. Im not sure if I just never noticed before though.I have a 2019, and have ford procal tune, airaid tube,mbrp catback, jlt catch can, blow off bypass valve,and I have changed the fuel pressure sensor. I have 28k miles and have changed my plugs 4x just to be cautious. This misfire started like a month ago and was really inconsistent,but now it does it every other day I have a pending misfire for cylinder 4 and first 1000 misfire. I want to get a compression test,but would like to know would the evap valve line cause this,as I have not changed that out yet? Thanks in advance.
 
#42 ·
Sorry to everyone that I did not follow up but I took the (smart/easy) way out. I took it to the mechanic and there was a slight crack in the head gasket. Just a bit of coolant was making its way into the cylinder. On top of that they found I believe some warping in the piston. Might have been more but I just decided to not continue listening as that was the last straw and I had made up my mind in selling the car. These engines are made of glass once you start modding them. I was able to sell the car and buy myself a Model S. It’s sucks because I really enjoyed this car but the problems just started to snow ball. This wasn’t the only issue with the car now. There were other little nuances that were creeeping up on just a two year old car. Take it to a mechanic but brace yourself for worst case. That way if it’s not then it won’t be as bad. Keep me updated on what happens with your car I’m very interested. I just preferred not worry about being a garage monkey on a new car.
 
#44 ·
Damn.. I hate to hear that. I wont even bother with the evap valve then. It sucks having that pending code and or code for cylinder 4 misfire. I think that would make this car an impossible sell. Being tuned I know Im going to have to pay for the damn thing sadly. Im really stressed about it,and am expecting the worst. I will keep you updated. Hopefully I can get it in to ford on Thursday or Friday when Im off from work.
 
#45 ·
Yeah I feel you. The issue had me so stressed that’s why I was able to decide to sell it so fast. Not only was my cylinder 4 on, cylinder 2 started the day before I took it to the mechanic. I was able to sell the car to car max of all places and since I had a Cobb tuner I was able to rest codes and luckily since I was driving the car they did not notice the issues. They actually gave me a really good offer but I think they really did not check the car. Yeah my repair for the car was reaching 2500-3k if I remember correctly. I just took that money and spent it on a new car with warranty. My car was out of warranty due to miles not years. I am really shocked how fragile these engines are. I’m not even considering buying another mustang in the near future over this. Just relax and take it as is. See what the mechanic says and go from there. Stressing will only make it worse. I know it’s impossible to not stress it but you have done all that you can. It’s in the hands of the mechanic now. It really left a sour taste in my mouth over Ford motors. Trust me. We are not the only ones that this has happened to.
 
#46 ·
Thanks a lot man I appreciate it. At this point I hope its just a head gasket. It seems like a slight leak just like what you had going on.I have a ford credit card with a good limit on it so I could deal with a $1000-2000 bill (I definitely wish I didn't have to though)but damn..I can clear the codes,I have a code reader and I can reset all those codes with the procal too. It will fail IM readiness though.If they didn't check it I could get away with it,but Im sure they would,but I will keep that in mind.If I could get close to what I owe (which I really doubt) I would strongly consider a Kia stinger or something like that. My orange fury ecoboost looks so good too,but damn 28k with a head gasket issue,thats ridiculous. Thank you again for all your insight. When I read your post when I was searching what my issue could be, everything I had going on was what yours was doing. I will definitely update this post when I get it checked.
 
#47 ·
I also had the option to put the repair on a card but then I thought about the pros and cons of doing that versus putting that 2-3k towards another car and for me it just made sense. Doing a job where you have to open up the engine is not just a simple fix. I feel that once you start messing with issues like that then the rest of the issues will start to snow ball. I got close to what I owed on teh vehicle so thats why it made sense for me to trade in as well. I actually test drove the Stinger and its a serious contender. Lots of fun from stock and you get a better warranty. Not to mention the extra space. I decided to go electric since I just moved into a place where I have a garage. Take your time and assess all your options. dont knock one out. It does seem pretty ****ty that at only 28K you get this problem.
 
#49 ·
Well.. I still havent got my car to Ford because they are so busy. I will be bringing it in on the 19th. I pulled the #4 plug and wrapped it in paper towels and I believe coolant came out of the plug after a while. Its reddish liquid so.. I put a new plug in and it lasted a little less then a week till it started misfiring on startup. No white smoke,very little coolant loss, drives normal,just eventually on startup it will give the misfire code. Today I put in a new plug again just so I dont have a coolant filled plug.I took my airaid tube off,hopefully when they eventually see its a head gasket they will replace it under warranty,but who knows. I will keep updated when I find out.
 
#52 ·
Well.. I took my car to Ford last Thursday. They claimed it was a coil. I knew it wasnt, I told them I was losing a bit of coolant and it only did gave me a misfire on startup. I told them I really think its a head gasket issue.They changed the coil under warranty and replaced the plugs.. 2 days later I got a misfire code in cylinder 4 again. So they want the car this Monday and will give me a loaner. They said..well maybe it is a blown head gasket.I dont know if it will be covered under warranty. It might be as they covered the coil. I will see though.
 
#53 ·
It is the head gasket. I was getting cylinder 3 misfire as well. I traded my ecoboost for a new 2020 GT mustang with a 75000 mile warranty. The research ive done seems like the Coyote is a bit more reliable,so Thats how I went. I got 23k for my ecoboost and had to put 3k negative equity,but not too bad.Thank you Alobos05 for responding throughout.