Another Hesitation / Stumble / Misfire / Fuel cut in boost / Under load Thread
10-09-2019, 04:39 PM
#1
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Another Hesitation / Stumble / Misfire / Fuel cut in boost / Under load Thread
*zips up flame suit*
Guys,
Longtime lurker, finally purchased my 3rd Miata, but this time I purchased someone else's "project".
I say project because owner #2 built it, had it professionally tuned at AEDynamics (259whp) and sold it to owner #3 with this slight misfire (who was in way over his head) who then sold it to yours truly.
Twice removed, I havent been able to get ahold of the previous owner (maybe I should give Toby a call?) however I am in Norcal, quite a ways away.
*insert typical newb post about doing tons of research and searching millions of threads with no luck here* I come to you in peace, please halp. First time diving into the world of tuning so bear with me.
Like many other threads I've found, the car reacts very similarly; at 1/4 throttle, itll rev throughout the tach with perfection. Mash the throttle and it feels like a stumble/misfire/fuel cut scenario. After weeks of tweaking AFR tables, messing with Accel Enrichment, and auto tuning through VEAL, it is better, but only slightly. In a similar thread, a user "Curly" offered a msq file for a base accel enrich and after trying that, my car wouldn't even start.
Plugs are gapped to .30, wires are less than 5k miles old along with the LS coils. Without being another "that guy" I tried checking all the basics to no avail other than the ground which is happening tonight. Overboost was already set to 16psi (car is only achieving 8psi) then turned off with no help.
I've run some logs and will upload both the tune that came with the car as well as one that I've developed after a few months of tweaking in which the car runs a bit better.
I noticed the PW spikes, I'm assuming that has a lot to do with it, but after countless videos I can't put two and two together on how to adjust *hangs head in shame* If there is a book on MS2, please point me in the right direction, I hate asking for help.
The Tunes with Accel Enrich are after the tweaks. The ones without are previous.
Mod list here:
94R 1.8 Stock internals / Head
6spd w/ 3.63 Torsen
Begi S6 w/ Garrett GT2860rs
DW 1000cc injectors
255lph Walbro
LS Coils
NGK BKR7Es
DIY MS2
Let me know any other information that is needed to diagnose.
Guys,
Longtime lurker, finally purchased my 3rd Miata, but this time I purchased someone else's "project".
I say project because owner #2 built it, had it professionally tuned at AEDynamics (259whp) and sold it to owner #3 with this slight misfire (who was in way over his head) who then sold it to yours truly.
Twice removed, I havent been able to get ahold of the previous owner (maybe I should give Toby a call?) however I am in Norcal, quite a ways away.
*insert typical newb post about doing tons of research and searching millions of threads with no luck here* I come to you in peace, please halp. First time diving into the world of tuning so bear with me.
Like many other threads I've found, the car reacts very similarly; at 1/4 throttle, itll rev throughout the tach with perfection. Mash the throttle and it feels like a stumble/misfire/fuel cut scenario. After weeks of tweaking AFR tables, messing with Accel Enrichment, and auto tuning through VEAL, it is better, but only slightly. In a similar thread, a user "Curly" offered a msq file for a base accel enrich and after trying that, my car wouldn't even start.
Plugs are gapped to .30, wires are less than 5k miles old along with the LS coils. Without being another "that guy" I tried checking all the basics to no avail other than the ground which is happening tonight. Overboost was already set to 16psi (car is only achieving 8psi) then turned off with no help.
I've run some logs and will upload both the tune that came with the car as well as one that I've developed after a few months of tweaking in which the car runs a bit better.
I noticed the PW spikes, I'm assuming that has a lot to do with it, but after countless videos I can't put two and two together on how to adjust *hangs head in shame* If there is a book on MS2, please point me in the right direction, I hate asking for help.
The Tunes with Accel Enrich are after the tweaks. The ones without are previous.
Mod list here:
94R 1.8 Stock internals / Head
6spd w/ 3.63 Torsen
Begi S6 w/ Garrett GT2860rs
DW 1000cc injectors
255lph Walbro
LS Coils
NGK BKR7Es
DIY MS2
Let me know any other information that is needed to diagnose.
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10-25-2019, 11:56 AM
#4
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Finally had time to bump this thread. Got ahold of Toby at AED and after countless tweaks and plugging new tunes in, setting timing, etc. Its been deemed that its got to be something mechanical.
Fuel Pump, filter, injectors... maybe wastegate causing this? Anyone experienced one of these causing this hesitation/stumble?
Fuel Pump, filter, injectors... maybe wastegate causing this? Anyone experienced one of these causing this hesitation/stumble?
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10-25-2019, 04:20 PM
#6
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The only way I can describe it is if I ease into the throttle, gradually all the way to floor, its fine. Pulls all the way to redline, boosts normally, etc.
Once I mash the throttle, in any gear, at any starting RPM below a certain threshold (out of the upper boost powerband), it hits this hesitation/fuel cut feeling. I can stay on it and it will eventually pull through, sputtering all the way there.
In mega-newbie fashion, I finally figured out how to read these logs and once I get home today I can see if I'm getting lean spikes or not. It would seem, though, that I'm getting too much or not enough fuel in this scenario. I.E. Foot to the floor, attempting to surge fuel into the system and misfiring/cutting out instead.
Tons of threads on this with no real solution other than overboost protection or plug gaps and neither is the cause here. I'll be diagnosing the fuel system tomorrow.
Once I mash the throttle, in any gear, at any starting RPM below a certain threshold (out of the upper boost powerband), it hits this hesitation/fuel cut feeling. I can stay on it and it will eventually pull through, sputtering all the way there.
In mega-newbie fashion, I finally figured out how to read these logs and once I get home today I can see if I'm getting lean spikes or not. It would seem, though, that I'm getting too much or not enough fuel in this scenario. I.E. Foot to the floor, attempting to surge fuel into the system and misfiring/cutting out instead.
Tons of threads on this with no real solution other than overboost protection or plug gaps and neither is the cause here. I'll be diagnosing the fuel system tomorrow.
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10-29-2019, 03:54 PM
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This sounds like incorrectly tuned VE or Accel Enrichment.
It is either going WAY rich causing a missfire when Accel Enrichment is trigger, or Accel enrichment is not configured at all.
You shouldn't start messing with Accel Enrichment until VE table is perfect.
I would say disable Accell Enrichment, disable auto-tune and go drive as smoothly as possible through all rev/load areas. So up hill in high gears, high speed in high and low gears etc etc.
Do that for a good few hours to get your table dialed in closer in case you've messed it up a bit.
Then, with the engine warm, in your sit there and give it fast blips from idle like 0-100% throttle in sub 1 second, the engine should stumble then rev.
Now, enable accel enrichment and start with some base values from the Adventures in EAE (or, Why do I abuse myself like this?) thread this should give you an idea of where to start.
With accel enrichment don't be focusing on getting your target AFR at tip-in (flooring it fast) instead you want response, this typically means running quite a bit richer than you normally would expect.
This also comes into play when going into boost fast because a similar thing can happen (large flow of air rushes in, ECU does not compensate, lean spike causes misfire, or ECU overcompensates, overrich condition causes misfire).
Please not, misfires show as lean whether they are due to a rich or lean condition, this is because the combustion is not occurring properly or at all. Don't trust your O2 readings when a misfire occurs, only know that a misfire has occured and start looking at your actual fuel pulse width values before and after the condition. I.e. if you are at 2k revs 10% throttle and running 1ms pulse width (completely random example number) then you increase throttle to 40% and it starts sputtering and you see it has gone to 40ms pulse width (40x the fuel with only a 30% increase in throttle) then you know its way rich, if the opposite happens and you go 10% to 40% but pulsewidth stays at 1ms then you can see that you have increased airflow but have no increase in fuel so your going lean.
This is how you can start to determine the cause of a misfire, the same occurs for ignition caused misfires.
It is either going WAY rich causing a missfire when Accel Enrichment is trigger, or Accel enrichment is not configured at all.
You shouldn't start messing with Accel Enrichment until VE table is perfect.
I would say disable Accell Enrichment, disable auto-tune and go drive as smoothly as possible through all rev/load areas. So up hill in high gears, high speed in high and low gears etc etc.
Do that for a good few hours to get your table dialed in closer in case you've messed it up a bit.
Then, with the engine warm, in your sit there and give it fast blips from idle like 0-100% throttle in sub 1 second, the engine should stumble then rev.
Now, enable accel enrichment and start with some base values from the Adventures in EAE (or, Why do I abuse myself like this?) thread this should give you an idea of where to start.
With accel enrichment don't be focusing on getting your target AFR at tip-in (flooring it fast) instead you want response, this typically means running quite a bit richer than you normally would expect.
This also comes into play when going into boost fast because a similar thing can happen (large flow of air rushes in, ECU does not compensate, lean spike causes misfire, or ECU overcompensates, overrich condition causes misfire).
Please not, misfires show as lean whether they are due to a rich or lean condition, this is because the combustion is not occurring properly or at all. Don't trust your O2 readings when a misfire occurs, only know that a misfire has occured and start looking at your actual fuel pulse width values before and after the condition. I.e. if you are at 2k revs 10% throttle and running 1ms pulse width (completely random example number) then you increase throttle to 40% and it starts sputtering and you see it has gone to 40ms pulse width (40x the fuel with only a 30% increase in throttle) then you know its way rich, if the opposite happens and you go 10% to 40% but pulsewidth stays at 1ms then you can see that you have increased airflow but have no increase in fuel so your going lean.
This is how you can start to determine the cause of a misfire, the same occurs for ignition caused misfires.
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11-06-2019, 03:54 PM
#10
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This sounds like incorrectly tuned VE or Accel Enrichment.
It is either going WAY rich causing a missfire when Accel Enrichment is trigger, or Accel enrichment is not configured at all.
You shouldn't start messing with Accel Enrichment until VE table is perfect.
I would say disable Accell Enrichment, disable auto-tune and go drive as smoothly as possible through all rev/load areas. So up hill in high gears, high speed in high and low gears etc etc.
Do that for a good few hours to get your table dialed in closer in case you've messed it up a bit.
Then, with the engine warm, in your sit there and give it fast blips from idle like 0-100% throttle in sub 1 second, the engine should stumble then rev.
Now, enable accel enrichment and start with some base values from the Adventures in EAE (or, Why do I abuse myself like this?) thread this should give you an idea of where to start.
With accel enrichment don't be focusing on getting your target AFR at tip-in (flooring it fast) instead you want response, this typically means running quite a bit richer than you normally would expect.
This also comes into play when going into boost fast because a similar thing can happen (large flow of air rushes in, ECU does not compensate, lean spike causes misfire, or ECU overcompensates, overrich condition causes misfire).
Please not, misfires show as lean whether they are due to a rich or lean condition, this is because the combustion is not occurring properly or at all. Don't trust your O2 readings when a misfire occurs, only know that a misfire has occured and start looking at your actual fuel pulse width values before and after the condition. I.e. if you are at 2k revs 10% throttle and running 1ms pulse width (completely random example number) then you increase throttle to 40% and it starts sputtering and you see it has gone to 40ms pulse width (40x the fuel with only a 30% increase in throttle) then you know its way rich, if the opposite happens and you go 10% to 40% but pulsewidth stays at 1ms then you can see that you have increased airflow but have no increase in fuel so your going lean.
This is how you can start to determine the cause of a misfire, the same occurs for ignition caused misfires.
It is either going WAY rich causing a missfire when Accel Enrichment is trigger, or Accel enrichment is not configured at all.
You shouldn't start messing with Accel Enrichment until VE table is perfect.
I would say disable Accell Enrichment, disable auto-tune and go drive as smoothly as possible through all rev/load areas. So up hill in high gears, high speed in high and low gears etc etc.
Do that for a good few hours to get your table dialed in closer in case you've messed it up a bit.
Then, with the engine warm, in your sit there and give it fast blips from idle like 0-100% throttle in sub 1 second, the engine should stumble then rev.
Now, enable accel enrichment and start with some base values from the Adventures in EAE (or, Why do I abuse myself like this?) thread this should give you an idea of where to start.
With accel enrichment don't be focusing on getting your target AFR at tip-in (flooring it fast) instead you want response, this typically means running quite a bit richer than you normally would expect.
This also comes into play when going into boost fast because a similar thing can happen (large flow of air rushes in, ECU does not compensate, lean spike causes misfire, or ECU overcompensates, overrich condition causes misfire).
Please not, misfires show as lean whether they are due to a rich or lean condition, this is because the combustion is not occurring properly or at all. Don't trust your O2 readings when a misfire occurs, only know that a misfire has occured and start looking at your actual fuel pulse width values before and after the condition. I.e. if you are at 2k revs 10% throttle and running 1ms pulse width (completely random example number) then you increase throttle to 40% and it starts sputtering and you see it has gone to 40ms pulse width (40x the fuel with only a 30% increase in throttle) then you know its way rich, if the opposite happens and you go 10% to 40% but pulsewidth stays at 1ms then you can see that you have increased airflow but have no increase in fuel so your going lean.
This is how you can start to determine the cause of a misfire, the same occurs for ignition caused misfires.
This is interesting, I'll get back to you on this.
Whats more interesting is that after I re-established timing, I went out on the Car's original Dyno-Tune and it stumbled a bit at first, but ran beautifully all the way up to 16psi. Car ran fantastic. Pulled it into the garage, said goodnight. (If its any note, here, the car began idling at 2100rpm after a few hard pulls).
Very next day, fired her up and noticed it was right back to where we were previously. Cruises great, any gear, any rpm, but one the gas is applied to accelerate the car it stumbles all the way up to redline. Boost holds, AFRs are a bit rich 11.5ish, but ti will slowly climb to redline.
I again reset timing, tried a few different tunes: both the safe base tune from Toby and the resulted dyno tune the car ran so well on previously, and nothing changed still a clockwork misfire under load.
Frustrating to say the least that under the same settings, same conditions, the car acts differently. I pulled the car over, dropped AE values slowly until it was completely off, car ran worse and worse and worse the lower my values got.
After rummaging through the net again, I found a video that most closely associated my symptoms (here is the thread with vids: http://www.miataturbo.net/engine-performance-56/breaking-up-bad-turbo-miata-82237/) and his had a few issues as a result:
1. He had stock coils and changing to a COP setup helped ( I am currently running low mileage LS coils with brand new .25 gapped BRK7Es)
2. He mentions a bad coil driver in the ecu. I have no idea how to go about checking for this, any links or suggestions would be appreciated.
3. In that thread, forum member sixshooter notices he may have selected the wrong MAP sensor in TS by citing: "it shows you are at 100kpa at 3530rpm at a very low throttle position. It shows you to have 12.2AFR there, which is still pretty rich. But I question if you really have 100kpa there. I still think you have the incorrect MAP sensor selected in your project setup menu.
Try an experiment for me. With the car off, turn the key to the "on" position and read in TS what the kpa reading is for us. And tell us your approximate altitude above sea level."
Something else I will have to check. If any of this sounds irrelevant, ill be buying new coils in hopes its just that.
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11-06-2019, 04:57 PM
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Have had the same issue but doesn't seem as bad as yours from your description. When I grab throttle from idle fast, it hesitates. A LOT of people seem to associate it with a bad AE/VE table, and say to retry for a better tune. It's more than that sometimes, and that's what it seems like you are experiencing too. Very interested in seeing how you fix it, it might fix mine too. It does seem like something mechanically wrong. Most logical thing I an think of would be fuel pressure. But when my pump went out a new one didn't fix the problem, maybe the regulator now.
Hope you fix it, always a b*tch when stuff goes wrong lol.
Hope you fix it, always a b*tch when stuff goes wrong lol.
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09-09-2021, 03:21 PM
#17
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did you ever find the fix? I don't have a miata but I do have a boosted 4 cylinder (93 mustang) on a diypnp. I have the EXACT same symptoms as you. Tried to post over on the megasquirt forum but they didn't seem like they cared much🙃
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09-09-2021, 03:28 PM
#18
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Hey man,
Ended up being the coils. Although they were new LS coils, they were chinese piles of ****. After a brief combo with MiataDad, I Figured a set of junkyard LS coils couldnt hurt. Sure enough, everything back to normal.
Do not buy chinese garbage.
Ended up being the coils. Although they were new LS coils, they were chinese piles of ****. After a brief combo with MiataDad, I Figured a set of junkyard LS coils couldnt hurt. Sure enough, everything back to normal.
Do not buy chinese garbage.
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09-09-2021, 08:13 PM
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09-13-2021, 07:08 AM
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I am new to tuning my car but was experiencing a misfire which was spark related. I am still using the oem wasted spark but I was researching dwell time to check that. There is a lot of different information about oem dwell time but some of it is actual measured values, so I increased the dwell when the coils were loaded and the misfire is either gone or a lot better , I have not tested enough to say it is gone but revs to the redline now. Anytime there is a different coil type I would think it might need a dwell time adjustment. Junk coils, all bets are off.
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