Help pls - VVT swapped 95, MS3X weird steady throttle surge+bucking+backfiring
11-08-2021, 12:26 PM
#1
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Location: Las Cruces, NM
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Help pls - VVT swapped 95, MS3X weird steady throttle surge+bucking+backfiring
Car is a 1995 with a 2000 engine, Trubokitty MS3X build. It's a recently completed track car project that unfortunately sits under the carport more than it gets driven these days. I've been able to do a few events with it this year but I never have my laptop with me and haven't had the time to diagnose what's happening. in the few street miles I've put on it it's doing this thing under "steady-throttle" where the AEM WB gauge goes full-lean and the car will kinda "surge", if that makes sense. At the track it's mostly good (not a whole lot of "steady-throttle" portions at our track) but it'll randomly hit what I can only describe as a "false limiter" where the car just kinda reaches a random RPM, usually 6500+, where it acts like it can't accelerate past it.
I took it out to a meet yesterday and it drove really great on the way there, aside from from the steady-throttle thing, but on the way back it started "bucking" randomly. I had my laptop with me, finally, so I got some logs! The log attached to this post is freeway speed, car bucking and backfiring really bad.
Listen, I'm extremely not good at this MS ****. I'm neither smart nor proficient in tunerstudio, just looking for some suggestions on things to troubleshoot. Thank you.
I took it out to a meet yesterday and it drove really great on the way there, aside from from the steady-throttle thing, but on the way back it started "bucking" randomly. I had my laptop with me, finally, so I got some logs! The log attached to this post is freeway speed, car bucking and backfiring really bad.
Listen, I'm extremely not good at this MS ****. I'm neither smart nor proficient in tunerstudio, just looking for some suggestions on things to troubleshoot. Thank you.
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11-08-2021, 06:22 PM
#3
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Join Date: Oct 2017
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A few things, you should be tuning with "Include AFR Target" under General Settings > Incorporate AFR Target.
This will stop your VE from reaching 150% which is due to you needing to lie to the ECU to get the AFR you want. (If you want to fix it without driving and retuning, you can enable it, then use (AFR From AFR table at this cell)/14.7 to find the percent that the VE will probably be off by, you can then multiply the VE at that cell by that number and it should bring you close, this will take some time with a calculator and your VE table and AFR table up.)
You will need to retune, but it will substantially improve tunability and allow your changes to AFR table to directly relate to fuel percent changes so if you want to go from 15.3 at cruise to 14.7 it just goes there.
For example, at 5000 RPM 180kPa your VE is 125.2, if you take the AFR you tuned for (tuned for without include AFR) it is 11.8.
11.8/14.7 gives us basically 0.8, if we multiply your 125.2 cell by 0.8 we get 100.2 which is much more reasonable for an engine around where it's peak torque would be.
I still think it might be a little off so that can be fine tuned but that is the just of it.
Although the end result seems the same it makes your life much much easier in the future when the ECU knows what is going on.
Now for your actual issue:
In terms of the log. You are hitting a lost sync counter of 86 by the end of that short log.
Your RPM drops to 0 multiple times as far as the ECU can tell.
The lost sync reason is 32 which is a Miata specific sync issue, 32 = Miata 99-00 - 0 cams seen
I.e. your CMP or Camshaft Position is disappearing.
Now I don't remember specifically how the late model engines are configured, but I believe you have a Crank sensor on the front of your Valve cover.
My mates NB was playing up and it was due to the Cam Position Sensor being loose and it was jiggling out sometimes.
So the issue is that your losing Camshaft signal somewhere or somehow, check sensor first, then connector, then cabling, then wiring to ECU.
Make sure you haven't got any of the sensor lines running near high noise items, Alternator, Ignition Coils/Ignition Power Wiring/Plug Leads, Injector wiring.
Also turn off Overrrun Fuel Cut for now so you can make sure things are tuned correctly and nothing else is cutting spark/fuel. It wouldn't show like this in the log if it was Overrun Fuel Cut, but I only turn things like that on after the engine is running very very well.
Fuel Settings > Over-run Fuel Cut > Off
This will stop your VE from reaching 150% which is due to you needing to lie to the ECU to get the AFR you want. (If you want to fix it without driving and retuning, you can enable it, then use (AFR From AFR table at this cell)/14.7 to find the percent that the VE will probably be off by, you can then multiply the VE at that cell by that number and it should bring you close, this will take some time with a calculator and your VE table and AFR table up.)
You will need to retune, but it will substantially improve tunability and allow your changes to AFR table to directly relate to fuel percent changes so if you want to go from 15.3 at cruise to 14.7 it just goes there.
For example, at 5000 RPM 180kPa your VE is 125.2, if you take the AFR you tuned for (tuned for without include AFR) it is 11.8.
11.8/14.7 gives us basically 0.8, if we multiply your 125.2 cell by 0.8 we get 100.2 which is much more reasonable for an engine around where it's peak torque would be.
I still think it might be a little off so that can be fine tuned but that is the just of it.
Although the end result seems the same it makes your life much much easier in the future when the ECU knows what is going on.
Now for your actual issue:
In terms of the log. You are hitting a lost sync counter of 86 by the end of that short log.
Your RPM drops to 0 multiple times as far as the ECU can tell.
The lost sync reason is 32 which is a Miata specific sync issue, 32 = Miata 99-00 - 0 cams seen
I.e. your CMP or Camshaft Position is disappearing.
Now I don't remember specifically how the late model engines are configured, but I believe you have a Crank sensor on the front of your Valve cover.
My mates NB was playing up and it was due to the Cam Position Sensor being loose and it was jiggling out sometimes.
So the issue is that your losing Camshaft signal somewhere or somehow, check sensor first, then connector, then cabling, then wiring to ECU.
Make sure you haven't got any of the sensor lines running near high noise items, Alternator, Ignition Coils/Ignition Power Wiring/Plug Leads, Injector wiring.
Also turn off Overrrun Fuel Cut for now so you can make sure things are tuned correctly and nothing else is cutting spark/fuel. It wouldn't show like this in the log if it was Overrun Fuel Cut, but I only turn things like that on after the engine is running very very well.
Fuel Settings > Over-run Fuel Cut > Off
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11-09-2021, 11:24 AM
#4
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Join Date: Apr 2011
Location: Las Cruces, NM
Posts: 590
Total Cats: 114
A few things, you should be tuning with "Include AFR Target" under General Settings > Incorporate AFR Target.
This will stop your VE from reaching 150% which is due to you needing to lie to the ECU to get the AFR you want. (If you want to fix it without driving and retuning, you can enable it, then use (AFR From AFR table at this cell)/14.7 to find the percent that the VE will probably be off by, you can then multiply the VE at that cell by that number and it should bring you close, this will take some time with a calculator and your VE table and AFR table up.)
You will need to retune, but it will substantially improve tunability and allow your changes to AFR table to directly relate to fuel percent changes so if you want to go from 15.3 at cruise to 14.7 it just goes there.
For example, at 5000 RPM 180kPa your VE is 125.2, if you take the AFR you tuned for (tuned for without include AFR) it is 11.8.
11.8/14.7 gives us basically 0.8, if we multiply your 125.2 cell by 0.8 we get 100.2 which is much more reasonable for an engine around where it's peak torque would be.
I still think it might be a little off so that can be fine tuned but that is the just of it.
Although the end result seems the same it makes your life much much easier in the future when the ECU knows what is going on.
Now for your actual issue:
In terms of the log. You are hitting a lost sync counter of 86 by the end of that short log.
Your RPM drops to 0 multiple times as far as the ECU can tell.
The lost sync reason is 32 which is a Miata specific sync issue, 32 = Miata 99-00 - 0 cams seen
I.e. your CMP or Camshaft Position is disappearing.
Now I don't remember specifically how the late model engines are configured, but I believe you have a Crank sensor on the front of your Valve cover.
My mates NB was playing up and it was due to the Cam Position Sensor being loose and it was jiggling out sometimes.
So the issue is that your losing Camshaft signal somewhere or somehow, check sensor first, then connector, then cabling, then wiring to ECU.
Make sure you haven't got any of the sensor lines running near high noise items, Alternator, Ignition Coils/Ignition Power Wiring/Plug Leads, Injector wiring.
Also turn off Overrrun Fuel Cut for now so you can make sure things are tuned correctly and nothing else is cutting spark/fuel. It wouldn't show like this in the log if it was Overrun Fuel Cut, but I only turn things like that on after the engine is running very very well.
Fuel Settings > Over-run Fuel Cut > Off
This will stop your VE from reaching 150% which is due to you needing to lie to the ECU to get the AFR you want. (If you want to fix it without driving and retuning, you can enable it, then use (AFR From AFR table at this cell)/14.7 to find the percent that the VE will probably be off by, you can then multiply the VE at that cell by that number and it should bring you close, this will take some time with a calculator and your VE table and AFR table up.)
You will need to retune, but it will substantially improve tunability and allow your changes to AFR table to directly relate to fuel percent changes so if you want to go from 15.3 at cruise to 14.7 it just goes there.
For example, at 5000 RPM 180kPa your VE is 125.2, if you take the AFR you tuned for (tuned for without include AFR) it is 11.8.
11.8/14.7 gives us basically 0.8, if we multiply your 125.2 cell by 0.8 we get 100.2 which is much more reasonable for an engine around where it's peak torque would be.
I still think it might be a little off so that can be fine tuned but that is the just of it.
Although the end result seems the same it makes your life much much easier in the future when the ECU knows what is going on.
Now for your actual issue:
In terms of the log. You are hitting a lost sync counter of 86 by the end of that short log.
Your RPM drops to 0 multiple times as far as the ECU can tell.
The lost sync reason is 32 which is a Miata specific sync issue, 32 = Miata 99-00 - 0 cams seen
I.e. your CMP or Camshaft Position is disappearing.
Now I don't remember specifically how the late model engines are configured, but I believe you have a Crank sensor on the front of your Valve cover.
My mates NB was playing up and it was due to the Cam Position Sensor being loose and it was jiggling out sometimes.
So the issue is that your losing Camshaft signal somewhere or somehow, check sensor first, then connector, then cabling, then wiring to ECU.
Make sure you haven't got any of the sensor lines running near high noise items, Alternator, Ignition Coils/Ignition Power Wiring/Plug Leads, Injector wiring.
Also turn off Overrrun Fuel Cut for now so you can make sure things are tuned correctly and nothing else is cutting spark/fuel. It wouldn't show like this in the log if it was Overrun Fuel Cut, but I only turn things like that on after the engine is running very very well.
Fuel Settings > Over-run Fuel Cut > Off
Like I said in the initial post, I'm so awful at the software side of things, I completely forgot MLV showed sync loss errors.
I've reworked the CPK+CMK harness a couple of times and I guess I just assumed I'd eliminated that as a potential issue. I'm gonna zip tie the **** out of them ala SM bois and see if that helps - otherwise I might look at Ballenger's units, even though the price makes me gag.
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11-10-2021, 04:29 PM
#5
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Location: Hollywood, FL
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SM bois solution is getting rid of connector at cam sensor. Take dremel, peel back hood and expose terminals, solder pre-tinned wires to them, and fill with epoxy or similar. You can do a connector a foot back or so or leave it hardwired since it's just a 6mm bolt to take off. You don't need expensive sensors, you just need a good connection.
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11-12-2021, 12:15 AM
#6
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Location: Las Cruces, NM
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Yeah I feel like that’s a better route that spending ballenger money on one.
I zip tied the **** out of mine and drove the car for a bit today - TS gauge only showed 2 sync loss events and they occluded during a startup so… ¯\_(ツ)_/¯
I zip tied the **** out of mine and drove the car for a bit today - TS gauge only showed 2 sync loss events and they occluded during a startup so… ¯\_(ツ)_/¯
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