Engine Misfire FBO Coyote

[mustangguy98]

Making this post after trying all other options to diag this misfire that I am having.
Car is a 15’ GT premium manual FBO E85. 18’ manifold, headers, exhaust, JLT CAI, LU47 injectors.

Recently got tuned for e85. I was on a Lund 93 tune with same mods for the longest time and had no problems at all with anything until I got on e85. mileage on car is 27,500. I’ve swapped coil packs around and installed fresh new NGK spark plugs and codes stayed in cylinder 2,3,4. took the car to the dealer and my guy recommended getting the computer flashed back to Ford stock and get retuned. originally I had Lund get the car back to stock. My guy at ford also said his device wasn’t responding to any of my computer’s modules... tried a compression test but couldn’t control my throttle body, performed misfire test and i was getting random misfires in all my cylinders.

I did what my guy recommended about reflashing the ECU and I am still having misfires at low RPMs about 1800k. Car seems healthy WOT and past 2k RPM. tuner said my O2 sensors were fine. I’ll say though after I got tuned on e85 I got a check engine light for the intake manifold runners as i left my tuners shop. He plugged his computer into the car and cleared the codes. shortly after that I got the check engine light for the random cylinder misfires. I’ve noticed that my air/fuel gauges have been off from normal. when i stepped on gas they go to 10 (lowest reading on gauge) when i let completely off the gauge goes to 20. If anyone can help me out with this issue and get it resolved that’d be greatly appreciated

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[TX5OH]

Making this post after trying all other options to diag this misfire that I am having.
Car is a 15’ GT premium manual FBO E85. 18’ manifold, headers, exhaust, JLT CAI, LU47 injectors.

Recently got tuned for e85. I was on a Lund 93 tune with same mods for the longest time and had no problems at all with anything until I got on e85. mileage on car is 27,500. I’ve swapped coil packs around and installed fresh new NGK spark plugs and codes stayed in cylinder 2,3,4. took the car to the dealer and my guy recommended getting the computer flashed back to Ford stock and get retuned. originally I had Lund get the car back to stock. My guy at ford also said his device wasn’t responding to any of my computer’s modules... tried a compression test but couldn’t control my throttle body, performed misfire test and i was getting random misfires in all my cylinders.

I did what my guy recommended about reflashing the ECU and I am still having misfires at low RPMs about 1800k. Car seems healthy WOT and past 2k RPM. tuner said my O2 sensors were fine. I’ll say though after I got tuned on e85 I got a check engine light for the intake manifold runners as i left my tuners shop. He plugged his computer into the car and cleared the codes. shortly after that I got the check engine light for the random cylinder misfires. I’ve noticed that my air/fuel gauges have been off from normal. when i stepped on gas they go to 10 (lowest reading on gauge) when i let completely off the gauge goes to 20. If anyone can help me out with this issue and get it resolved that’d be greatly appreciated

A/F ratio going to 10 under WOT for e85 is normal. Likewise going to 20 when getting completely off of it is normal. Mine goes into the 9’s on e85.

Are you using the pigtails to keep the imrcs? I’ve heard that they are prone to not working properly sometimes. So perhaps that triggered the irmc light. Have you tried locking them out and getting your tune updated for them to be locked out to see if that fixes it?A faulty imrc control can cause it to be in the wrong position and if so will trigger misfires.
Is it misfiring at WOT and high rpm or just down low?

 

[mustangguy98]

A/F ratio going to 10 under WOT for e85 is normal. Likewise going to 20 when getting completely off of it is normal. Mine goes into the 9’s on e85.

Are you using the pigtails to keep the imrcs? I’ve heard that they are prone to not working properly sometimes. So perhaps that triggered the irmc light. Have you tried locking them out and getting your tune updated for them to be locked out to see if that fixes it?A faulty imrc control can cause it to be in the wrong position and if so will trigger misfires.
Is it misfiring at WOT and high rpm or just down low?

I am using lockouts for the IMRCS. i pulled the intake off and confirmed that they are still locked out. the tune is accommodating the lockouts. still getting misfires and unsure what it could be. thinking about just buying new coil packs

 

[TeamDenno]

Your misfire issue sounds remarkebly similar to my experience.

17 Car, 18 Mani (IMRC lockout). LU47's. Lund 85

The car performs brilliantly normally. Under WOT and on the track - no drama. Using the car mashing up and down the rev range... just performs with out issue

But if I use cruise control on the freeway on about 1800rpm in 6th (6MT), i get "Misfire Cyl 8"on the DTC's.

Interestingly, that has not triggered the engine warning light.

 

[mustangguy98]

Your misfire issue sounds remarkebly similar to my experience.

17 Car, 18 Mani (IMRC lockout). LU47's. Lund 85

The car performs brilliantly normally. Under WOT and on the track - no drama. Using the car mashing up and down the rev range... just performs with out issue

But if I use cruise control on the freeway on about 1800rpm in 6th (6MT), i get "Misfire Cyl 8"on the DTC's.

Interestingly, that has not triggered the engine warning light.

Did you figure out what the issue was? i moved the coil packs around and the code stayed in cylinder 2 and code for misfire at startup so i just bought some ford performance coil packs. hopefully that fixes the issue.
The car performs great WOT as well, it’s just misfiring at cruising speeds where i’m around 1,800-2,300 RPM, you can hear the exhaust break up at this range

 

[TeamDenno]

No. Haven't solved yet.

Haven't taken into my mechanic for a looksie yet.

Have a track day coming up, so want to see if anything happens under continued heavy use.

 

[Jhamp232]

Chiming in to mention a similar situation and share the details.
Background details: I've got a '15 that I installed LU47s and a 2018 intake manifold on last year (car is a seasonal driver) around august. IMRC locked out, also tuned for flex fuel. I travel for work and when I'm home the Mustang only sees split time daily use. Also, I do the tuning myself via HP Tuners.
Drove last season with no CEL. Around May this year I got P0300/P0308. Clear codes, they come back a month/1k miles later. I use HP tuners to monitor misfires since startup to see what's going on and log commute. Car is only missing around 1500-2000RPM/low load. If driving 10% throttle at 2000RPM the misfire counter ramps sky high, tip-in throttle and misfire counter stops dead in it's tracks.
With life being busy I didn't have the time to troubleshoot, so I threw the 2015 intake manifold back on because it takes like 20 minutes. No more CEL, misfire counter proves the repair.
Now, keeping in mind that I fabbed up sealing plates to leak check my 2018 manifold before I installed it, I have a hard time believing this is an intake leak issue. I'm guessing I need to clean up my MAF transfer, or lock the calibration out of some mapped points where it would normally utilize the IMRC. Unfortunately for me, I've got 714 other projects to complete before my wife blesses me with another kiddo. I still have not re-leak checked the 18 manifold, and I never have time to calibrate as it can be very time consuming not being on a dyno and all. I'm hoping to find a day to get this done soon (I've been saying that since May) and if I do, I'll follow up. Until then, I hope the additional case study benefits your troubleshooting.

 

[TeamDenno]

Drove last season with no CEL. Around May this year I got P0300/P0308. Clear codes, they come back a month/1k miles later. I use HP tuners to monitor misfires since startup to see what's going on and log commute. Car is only missing around 1500-2000RPM/low load. If driving 10% throttle at 2000RPM the misfire counter ramps sky high, tip-in throttle and misfire counter stops dead in it's tracks.

Sounds like exactly the same issue I have been having. I have narrowed mine down to usin cruise control on the freeway.

I'm just back from a 400km roundtrip day out where each way included a 100km freeway stretch at 110kph. On this strip I didnt use cruise on the freeway, and regulated throttle the old fashioned way (my foot!) and have no P03xx codes thrown at all. Every time I get a code, I'm on the freeway at low rpm in 6th.

Wierd hey?

 

[mustangguy98]

So just to update this post, i’ve tried almost all methods to diagnose this misfire. After resetting the computer and getting a new tune, to changing spark plugs, cleaning fuel injectors, checking lockouts on manifold and installing brand new ford performance coil packs. I am still receiving CEL codes p0300, p0316, and p0302. Very frustrating as everytime i’m cruising the car sounds ugly with the exhaust breaking up around 1,800-2,300 RPM. running out of options and debating on taking it to a performance shop for a different professional opinion.

 

[XeninWorX]

Similar to a problem I had with my 2006 Civic Si. Car would bog sometimes at low RPM and also on the highway. I’d be sitting in a drive through and the car would feel like it was gonna die. Could give it all the gas I wanted but wouldn’t accelerate. Had a buddy run a diagnostic on it and turns out I had a misfire on one of the cylinders. So since my buddy had the same Civic Si, we swapped his injectors into mine. Car ran perfect. Luckily found someone selling low mileage injectors on the Civic forum and never had the problem again.

 

[mustangguy98]

Similar to a problem I had with my 2006 Civic Si. Car would bog sometimes at low RPM and also on the highway. I’d be sitting in a drive through and the car would feel like it was gonna die. Could give it all the gas I wanted but wouldn’t accelerate. Had a buddy run a diagnostic on it and turns out I had a misfire on one of the cylinders. So since my buddy had the same Civic Si, we swapped his injectors into mine. Car ran perfect. Luckily found someone selling low mileage injectors on the Civic forum and never had the problem again.

hmmm these LU47 injectors are brand new. i’ll tell you what though, i left them brand new in the box in a storage unit over the summer, maybe that might’ve did something but i doubt it since they should withstand high engine temps. this problem only started happening after injector install and new e85 tune.

 

[XeninWorX]

hmmm these LU47 injectors are brand new. i’ll tell you what though, i left them brand new in the box in a storage unit over the summer, maybe that might’ve did something but i doubt it since they should withstand high engine temps. this problem only started happening after injector install and new e85 tune.

so then it’s either the tune or the injectors or both. I’m leaning towards injectors. Those things need to be precise and the opening is tiny.

the reason I had a misfire from the injector was because I hydrolocked the motor. That motor still runs perfectly fine, surprisingly. Somehow it damaged 1 injector. I think it was the 1st one, which is all the way to the left. So the water went through the intake manifold and hit that runner first. All it needed was a good injector and been running fine ever since. That happened back in the early 2010s. Sold the car last year to buy the Stang.

 

[Jhamp232]

Well, my issue is definitely not injector related, otherwise the PID misfires since startup would not have stopped seeing misfires after reinstalling 2015 intake manifold. Still running LU47s issue free. I’ll get to reinstalling 2018 manifold soon, but for now, gotta watch Lomachenko v Lopez.

 

[XeninWorX]

Assuming the injectors are good then quite possibly the tune or may even be the gas station you’re getting the fuel from. Not unheard of of getting bad gas. Here in Canada we have winter and summer gas which are different blends.

 

[mustangguy98]

Assuming the injectors are good then quite possibly the tune or may even be the gas station you’re getting the fuel from. Not unheard of of getting bad gas. Here in Canada we have winter and summer gas which are different blends.

yeah im very unsure, i’ve gotten 5 revisions since i started getting this issue to ensure it wasn’t a tuning problem. i have strong confidence in the tuner, very credible. currently has the 2nd fastest N/A coyote f150 in the world, mechanical engineering degree and no one i know has had any issues with his tuning. my last resort is to take it to a local coyote performance shop so they can tear it apart and figure out if there’s anything wrong. i recently pulled out a spark plug to inspect and noticed there was oil around the thread. unsure if this is related to my misfire

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