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Odd Misfire Issue

6K views 76 replies 11 participants last post by  Spectre71 
#1 ·
I’m having a misfire issue after installing cvfab race intercooler. I was on stage 1 Cobb tune before the intercooler and at max had a misfire count of 3 on cold start occasionally and never any negative ignition correction. Immediately after the install I started it up and misfire count went high as well as negative correction so I reset the ecu thinking it needed to relearn or such. Which of course after it ran quite a bit better but now I get misfire count up to about 50 to a 100 depending on how many pulls I do. This is within a 30 min drive. However I rarely see negative ignition correction and when I do it’s max -2. I would also note that I never feel or notice the misfires either. I will post a data-log of a run after work.
 
#3 ·
Check engine light on, any DTCs being set.

BD
 
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#6 ·
Make sure the sensors o ring did not get nicked or cut when installing in the IC and that it is fully seated flush in the IC and screw is tight. Lube the o ring with some light oil to help it slide into the IC.

BD
 
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#8 ·
It's not likely a minor boost leak should cause a misfire, but it is possible. I am surprised there is no DTCs being set though.

Are the misfire counts being set only at WOT or at part throttle as well?

If you brake load the engine, do you feel any misfires or does the cobb show misfires occurring.

What is your max boost pressure at WOT pull.

BD
 
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#10 ·
It's not likely a minor boost leak should cause a misfire, but it is possible. I am surprised there is no DTCs being set though.

Are the misfire counts being set only at WOT or at part throttle as well?

If you brake load the engine, do you feel any misfires or does the cobb show misfires occurring.

What is your max boost pressure at WOT pull.

BD
It seems as though I get maybe 1 every now and then at partial throttle but for the majority it’s all full throttle. Brake load the engine as in downshift(engine braking)? I just get loud noise and a few pops from my burble tune but that it is nothing odd. The max boost I am seeing at WOT is a couple decimals over 25psi. May I also note that I drove the car in the heat of texas just a few minutes ago and reached 8 misfire within a span of 25 minutes but only went WOT a few times. I do notice that perhaps the misfire is more common in cool weather like at night or perhaps it’s just a fluke. I’ll have a data log coming your way soon, thank you!
 
#12 ·
By brake loading the engine I mean at a stop with foot firmly on brake apply throttle to see if you can feel the engine misfiring since in your first post you stated you do not feel any misfires. Brake loading will allow you to feel if the engine misfires without road inputs when driving, you can go to 1/2 to 3/4 throttle for brief periods (less than 15 seconds at a time) for 2 or 3 times to see if you actually feel a misfire occurring.

Also do as Horcy1 states check plugs, coil connections and coil boots that attach to the plugs for issues or damage.

The fact that the issue is occurring after the IC install means you need to double check all the work you did installing it for loose connections or other connectors or hoses getting knock loose or damaged.

BD
 
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#9 ·
Have you checked your plugs haven't backed out ?
How many miles on your plugs. ?
Are they gapped accordingly ?
Do you have the correct heat range ?
 
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#14 ·
"pops from my burble tune but that it is nothing odd. The max boost I am seeing at WOT is a couple decimals over 25psi"

I'm a little confused, how did you get a burble tune on your car while running an OTS Cobb tune?

"I was on stage 1 Cobb tune before the intercooler"

I'll amit, I don't understand everything a Turner does to create a burble tune, but I'm guessing it has nothing to do with engine performance.
And did you install the OTS stage 2 tune after installing your Intercooler?
 
#18 ·
"pops from my burble tune but that it is nothing odd. The max boost I am seeing at WOT is a couple decimals over 25psi"

I'm a little confused, how did you get a burble tune on your car while running an OTS Cobb tune?

"I was on stage 1 Cobb tune before the intercooler"

I'll amit, I don't understand everything a Turner does to create a burble tune, but I'm guessing it has nothing to do with engine performance.
And did you install the OTS stage 2 tune after installing your Intercooler?
PD tune offers burble tune added onto any cobb tune of your choice. I have not installed the Stage 2 however i will try it if you recommend it? I have stock intake box with a k&n filter, CvFab Race intercooler, 1 step colder plugs, Borla Atak Cat Back, as well as CvFab Charge Pipes.
 
#17 ·
Keep us informed.

BD
 
#22 ·
These plugs can be gapped. Nothing special about them. You just have to be careful that's all.
 
#29 ·
I have a pro tune with a burble tune. Had it 2 or 3 years now. No issues so far. Can even have more then one map with it. You just can't have one map with and one map without for some reason.

I haven't got a clue what my BHP as the AP best BHP should really be a feature that should be removed and as such taken with a pinch of salt. My torque however is over 500 ft lbs
 
#35 ·
Yeap that would do it. I'm surprised that an upgraded IC is woefully under performing.
 
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#37 ·
That’s odd, it feels as though the intercooler is working wonders. The car doesn’t feel like it’s heat soaked either.
So, you bought a burble add-on for stage 1 and had misfires, then switched to stage 2 and the misfire issue went away? Do you think perhaps the burble tune could have been the cause of the misfires?
Incorrect. Both Stage 1 and Stage 2 have misfire. Burble tune doesn’t seem to have any effect what so ever on the misfire count.
 
#41 ·
I cannot see the datalog files that were attached so do not know exact IAT1/IAT2 temps were in the logs.

I just got back from the Hot Rod Power Tour that consisted of 1500 miles in 5 days stopping at 5 different cities for car shows and events. The ambient temps for those 5 days were 100 degrees with heat indexes of up to 110 degrees and my IAT1 was 107 to 115 with IAT2 from 115 to 125 while cruising on the interstates at 70/80 mph with a CVFab IC, when idling in lines to get into events my IAT1 would creep up to 150 degrees and IAT2 up to 160 degrees. This is just for a reference of where the IC should keep IATs at so roughly 10 degrees or less above ambient for IAT1 and within 10 to 20 degrees above IAT1 temp for IAT2 temps when at cruising speeds is my experience. Of course, the cooler the ambient the lower the spread of the IAT1 and IAT2 should be.

BD
 
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#49 ·
Plugs look good with no signs of damage or excessive oil/carbon deposits. Were any loose in the head, what do the coil boots look like, any sign of damage to them. Were the wire connectors secure on the coils.

BD
 
#52 ·
What air intake do you have. Is it a CAI pod filter?
 
#54 · (Edited)
I don't do google at all in any form so cannot see your datalogs, so cannot be of any help based on them. Sorry.

If this started after IC install my gut and years of experience tells me there was something either done during install or missed that is at the root of the misfires. If it was occurring before the install, then unsure at this point.

Did your car have grill shutters that you had to remove to install the race IC or were there no shutters. If it had shutters and you removed them leaving the connector for them disconnected, then there should be a DTC set for that issue. Removing them and leaving the connector disconnected will not turn on the CEL but will set a DTC for them. You stated you see no DTCs being set via the cobb AP so if it had shutters and still no DTCs there may be an issue in the PCM or with the cobb tuner.

BD
 
#55 ·
Here is a Dropbox link for the last data log I posted DATALOG. Also yes I do have a DTC for the active shutter however no other DTC at all. I also just pulled the bumper, firmly reassured the sensor was connected and tightened down every clamp as tight as possible. May I note when I initially installed the intercooler and charge pipes about a minute after letting the vehicle idle and then run I gave it about 3/4 throttle from a stop and the throttle body rubber boot shot off as I forgot to tighten down the clamp. Do you think that may have caused internal damage in any way going from almost WOT to zero boost? I also noticed I am again lower on coolant after about 3 weeks and filled up to the max line now so perhaps the early stages of a head gasket leak. Still no white smoke, and I’m looking for a pressure kit and compression kit to rule that out. I may also switch to msd coils to rule that out as well.
 
#62 ·
Methodical is definitely the correct approach to pursue by only changing one thing at a time to see if it makes a difference and corrects the problem. Changing more than one thing at a time will make it impossible to actually determine what the root cause is of the problem.

Just as a test try unplugging your IAT connector at the airbox to see if the PCM sets a DTC for it so you know the computer is responding correctly by starting the car and letting it run for a few minutes until the CEL comes on.. If it does not set the DTC for an IAT then you may have a PCM issue, but if it does set a DTC then yuu know it is operating properly.

BD
 
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#63 ·
Methodical is definitely the correct approach to pursue by only changing one thing at a time to see if it makes a difference and corrects the problem. Changing more than one thing at a time will make it impossible to actually determine what the root cause is of the problem.

Just as a test try unplugging your IAT connector at the airbox to see if the PCM sets a DTC for it so you know the computer is responding correctly by starting the car and letting it run for a few minutes until the CEL comes on.. If it does not set the DTC for an IAT then you may have a PCM issue, but if it does set a DTC then yuu know it is operating properly.

BD
Okay, so correct me if I’m wrong
1st: Disconnect IAT and check for DTC
2nd: Switch to stock tune and check for misfire
3rd: Replace spark plugs and check for misfire
4th: Replace Coil Packs and check for misfire

I would also like to note when I removed the coil on cylinder 1 I did notice a bit of white dust/powder/corrosion on the boot.
 
#64 ·
That would be my approach after I was 100% sure there is no issues from the IC install.

The white dust/powder on #1 boot could be indication of oxidation from moisture getting past the top of coil pack seal to valve cover which could lead to misfires.

BD
 
#65 ·
That would be my approach after I was 100% sure there is no issues from the IC install.

The white dust/powder on #1 boot could be indication of oxidation from moisture getting past the top of coil pack seal to valve cover which could lead to misfires.

BD
I disconnected IAT and it did show a DTC! So next I placed new plugs gapped to .028 and immediately noticed the car ran smoother. So I went for a drive, misfire count went to 4 then until I got on the highway and WOT which it shot up to 55 with -3 ign correction so I pulled over, reset the ECU learning and then did a few WOT runs with the misfire count only going up to 6 which is normal to me. What wasn't normal was the constant negative ignition correction on all cylinders between -1 and -4. So I flashed cobb stage 1 instead of stage 2 and have since noticed zero ign correction and a max misfire count of 6. I will also attached a datalog of a pull I did on Stage 1 with my new spark plugs after the ECU reset.

Here are a few different ways to access the datalog in case anyone doesn't use google or such.

Google DATALOG
Dropbox DATALOG
Filebin DATALOG
Icloud DATALOG
 
#67 ·
All the coil boots look the same, so I don't think it's a moisture issue. I believe it's just the interaction between the rubber and the aluminum of the head from heat cycles causing some migration of aluminum oxide dust to accumulate on the ends of the boots.

Nor sure what the actual difference between stage 1 and 2 is on the cobb tuner but it seems that stage 2 is not happy in your car.

BD
 
#68 ·
All the coil boots look the same, so I don't think it's a moisture issue. I believe it's just the interaction between the rubber and the aluminum of the head from heat cycles causing some migration of aluminum oxide dust to accumulate on the ends of the boots.

Nor sure what the actual difference between stage 1 and 2 is on the cobb tuner but it seems that stage 2 is not happy in your car.

BD
Yeah seems so, how about the data log? Anything look wrong? Thank you for all your help as well!!
 
#69 ·
Other than the negative IGN corrections it all looks pretty good. Not sure on why so much negative corrections other than possible poor quality tank of fuel. Did you just get fuel before this issue started and it was just a coincidence that you installed the IC after filling up.

Do you use top tier fuels or just 93 fuel from cheapest places. One tip is never get fuel from a station if you see the tanker dumping fuel into the stations tanks. It stirs up all the dirt/crud from the bottom of the big tanks which takes 24 hours to settle back to the bottom of the tank.

BD.
 
#70 ·
I use the best gas I can find, I believe this tank is from shell and of course 93! However I have noticed that this specific QuickTrip gas station reacts extremely well with my tune and is usually a few cents cheaper than shell. In fact this station reacts better than any other gas I’ve ever had in the vehicle, I think I’ll fill up with that and go from there. Are there any other factors that could cause negative ignition correction? Also thanks for the tip! Never thought about that but makes perfect sense. Also I’ve filled up multiple times since the intercooler install…I tend to drive allot.
 
#71 ·
Quicktrip is a top tier station so if your car likes it then keep using it, feed her what she likes best.


I did notice that when it was in negative corrections the AFR was a bit rich so it may have been just the PCM doing its job of managing timing based on fueling and air flow/temps.

I would just keep an eye on the misfire and corrections to see if over time the adaptive learning of the PCM strategy will sort things out on its own.

BD
 
#72 ·
Quicktrip is a top tier station so if your car likes it then keep using it, feed her what she likes best.


I did notice that when it was in negative corrections the AFR was a bit rich so it may have been just the PCM doing its job of managing timing based on fueling and air flow/temps.

I would just keep an eye on the misfire and corrections to see if over time the adaptive learning of the PCM strategy will sort things out on its own.

BD
Alrighty, Thank you again for all your help!! I’ll give you an update in about a day or two on how she’s running.
 
#73 ·
(y)

BD
 
#74 ·
Check your spark plugs. Make sure you have the right gap. Also, try one step colder plugs like the NGK most of us use.
If you are running a stage 1 93 octane map, use the stage 1 91 octane map with only 93 octane in the tank. It may be possible that the local stations have poor gas. I would suggest having the gauge: Knock Octane Modifier on your accessport so you can easy if it is bad fuel. Most of us have gone through the same issues, so we all help each other diagnosing the source of issues.
 
#76 ·
The last time I got a bad tank of gas was at a QT station...
 
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