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erroneous trigger causing ignition cut and erratic tach


S4-VR6
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Hello,

I was hoping to get some help on a trigger error.

Motor is VW MKIII Vr6                                

I started to experience what seemed to be an ignition cut while at mid range RPM. I noticed that when it would go into this cut mode the tach in the software would bury itself at 8k (max) momentarily then return to actual engine RPM. When it did this I received an RPM limit activated error and the ignition cut the same way it does when I actually hit the RPM Limit. My first thought was that the crank position sensor was starting to act erratic, but I am not convinced.  

Observing the run time values I am seeing trigger errors starting around 3800-4000 RPM and increasing until the engine falls below 3800 RPM. Since day one I have always had a miss at idle that I have not been able to tune out The car starts pretty easy and does not miss at idle for the first 10-15 seconds when its cold, then the miss picks up and does not go away throughout the ECT range. 

I would be greatly appreciative if you could take a look to see if anything jumps out and to lend a suggestion or two at what to look at next. Attached are a couple logs. The larger file is a non aggressive driving log. The smaller file is me revving the engine in neutral to demonstrate the problem and is probably a little more to the point.   

 Any help is most appreciated.

 Kind regards,

Bob O

IMG_1400 (1).jpg

Log 20-07-21 6_52_03 pm.zip Log 20-07-21 7_05_59 pm.zip

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It appears you have a V series ecu, not an i series, so there is no built in trigger scope.  You will need to get someone with an oscilloscope to do a quick capture of the cam and crank signal to see what it is not happy about.  

If you attach a copy of your tune I will take a quick look at your settings, but I would say it is more likely a waveform problem rather than settings problem.

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Hi Adam, 

you are correct, I do have a V series. My apologies. 

I have access to an O-Scope, I will try to hook it up and get a signal capture. If it is a waveform issue, what would be the tell-tale within the waveform and what can I do to remedy it?  

I have tried changing filter levels on the triggers but did not seem to change anything. Could it be a trigger calibration issue? Could it be spark plugs? Have you seen similar issues were it looses its mind at higher RPM and regains composure when the RPM comes back down?   

I tried to attach a zipped file of of a data log. Here is a second attempt.   

Thanks very much!

Bob O

Log 20-07-21 7_05_59 pm.zip

Hi Adam, 

Attached is a tuning .pcl opposed to a log, maybe this is better? 

thank you again,

Bob O

S4-VR6_150_A_Rev_3.2.1.pcl

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Just give us a photo or screenshot of an oscilloscope capture at idle.  

I see you have trigger 2 set to cam pulse 1X.  Does it really only have a single tooth on the cam?  Our notes say the VR6 engine has 4 teeth on the cam and you need to use the Holden trigger mode.  I know there are a couple of different generations of these engines tho.  Google images seems to show the Mk3 VR6 has 4 teeth too.

rU3q9Tm.png

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Hi Adam, 

Excuse me if this is trivial but I do not see an option for a Holden Trigger mode and there is no option of cam pulse 4x? How can I set it up as you suggest? I am sure my cam has 4 teeth the photo indicates. 

I hope its as easy as a setting. 

Thanks Very Much!!! 

Bob O

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Hi Adam,

I now see the option for the trigger mode to be set up as Holden V6 Alloytec III VVT but not the Ecotech as suggested in the attached PDF (I wish I had found that earlier). I also was under the impression that VVT was for variable valve timing, which I do not have so I never investigated. 

I can change all my setting to match this PDF no problem but I am confused on the DI 1-4 and the Aux 1-4 set up. I have my cam position sensor wired to trigger two and not to DI 1-4 and I do not have a VVT solenoid to wire to Aux 1-4? VR6 Engine Specific Info for Vi-PEC.pdf 

I also noticed my ignition set up did not match the PDF and I was not applying a delay. I will also correct this to match the PDF and try to measure the delay per the instructions. How does this correlate to the Trigger Offset, which one needs to be adjusted first (they seem to do similar things)? 

When I started this project I had no clue what to look for when building the motor and what to apply to the software... probably pretty obvious. I can tune fuel and ignition timing, its all the other small details that I lack experience in. 

I feel like I am close!

Thanks again!!

Bob O  

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Set the trigger offset at fast idle so that the timing mark matches your reference timing value.  Once that is done, rev the engine to high RPM to confirm the timing mark doesnt drift off the reference for the whole RPM range, if it does you adjust the drift out with the offset value.  

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Hi Adam,

I adjust the drift with the delay correct, not the offset? I thought the offset would change my idle timing.   

what about the:

Alloytec vs Ecotech? I dont have Ecotech as an option? 

Does VVT stand for variable valve timing? That is a confusing trigger mode since I do not have variable valve timing. Do I need to perform the VVT set up or is that to determine the trig 2 offset which is 74 ATDC according to the pdf. How does the 4 cog cam come into play? 

My main ignition offset in the calibration screen is currently 275, could that make sense (not very close to the approximate 9 in the pdf)?  

Lastly, what about the digital inputs and auxiliary outputs? I am not sure what to do with those setting.  Did I read/interpret correctly that since my cam position sensor is wired to trigger 2 that I do not need to configure a DI for the cam sensor? 

 

Thank you sir, your help is truly appreciated!! VR6 Engine Specific Info for Vi-PEC.pdf

 

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If your engine doesnt have VVT then you dont need to configure it.  You will not have any DI's or auxes set to VVT if you dont have VVT.  The correct trigger mode is Holden Alloytec iii.  

Offset needs to be checked with a timing light.  It will be different for different trigger modes, I would expect it to be close to the value quoted in the help file in most cases.

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After adjusting the settings to mimic the help file the motor barely ran (very rough idle and would not rev easily, seemed like ignition timing was way off, no backfires either way)  and I was accumulating trigger errors slowly.  

I have a stock coil pack that is a single brick with 6 wire outputs. Direct spark seemed to make sense but it likes wasted spark a lot better, not sure what the internals are.  I did replace  spark plugs not long before this issue seemed to appear, but to be honest, I am not sure how long the problem has been there, unknown to me... 

I was hopeful that this was going to solve the problem, what do you recommend next? Do you believe it is in software or physical? would replacing both sensors be worth while? 

Thanks!

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On 8/10/2021 at 10:04 AM, Adamw said:

You will need to get someone with an oscilloscope to do a quick capture of the cam and crank signal to see what it is not happy about.  

 

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Ok, 

I will hook it up to my O-scope at work and get some screen captures, hopefully this week.  

What do you want to see? The help file configuration that barely kept the engine at idle or my configuration where the engines runs better. At idle, rev'ed to where trigger error starts, etc.? I would prefer to only have to do this once if possible so any guidance will help. 

what potential "things" will make it unhappy? 

Thanks very much!   

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Just a capture at idle will be fine.  ECU settings will make no difference to the waveform the sensors are outputting.  

 

6 hours ago, S4-VR6 said:

what potential "things" will make it unhappy? 

Number of teeth on the cam, position of teeth in relation to the crank, the high and low voltage levels.  On the crank we want to confirm arming threshold is suitable for the voltages present, any ground offset, the polarity is correct and the zero crossings are sharp.

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Sounds good. 

Do I need to adjust any parameters like arming threshold and capture the affect or can we determine all pertinent values from the capture at idle? If all I need to do is capture the signals at idle, no need to reply. I am planning on hooking it up the scope tomorrow. 

Thanks!!

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Hi Adam, 

Attached are a few photos of the O-Scope signal i was able to capture. take a look and let me know what jumps out and what I can address to remedy. 

Thanks very much!! 

IMG_1458 (1).jpg

Hi Adam, 

I forgot to mention that scope A was wired to the cam sensor and scope B was wired to the crank sensor. 

Thanks, 

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Maybe the falling edge of the cam being too close to the missing tooth from the crank. But you said there are 4 teeth so maybe that's not the issue. 

Wondering if the crank isn't wired backwards. But that's also just a guess :D

wait for a real answer from Adam 

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Yes, crank sensor is wired backwards, swap the +/- wires at the crank sensor plug.  Hard to see how many teeth are on the cam, but stick with the Holden mode for now and see how it behaves with wiring corrected

Also Channel A (cam) shows only 0.5V, which is not acceptable, Is it possible you had the probe set to 10X or maybe had an attenuator connected?

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Thanks Gents!

I will correct the wiring, that's an easy fix.

sure as sh!t, the probe I was using was a 10:1. I assume this should be a 0-5v signal? I will roll the wires, adjust my probe, and grab another capture this weekend.

Looking at probe B, it is also a 10:1... does that make sense or are all bets off due to wiring issue? What should its voltage be?  

Thank you again!!! 

Bob O 

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Hi Adam,

I rolled the crank position sensor wires as suggested and my trigger error at high RPM is gone!!! 

I tired to run the configuration available in the help file we have discussed and it still would barely idle. The car is running better than ever using my config and seems pretty close. Any ideas why? 

Attached is the updated waveform with the newly wired crank sensor. It seems to have changes the cam sensor profile as well, is that what was expected? 

If you could let me know how this looks and if I need to address any other anomalies.  

Thanks!! 

Bob O   

IMG_1466.jpg

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You have cross talk between your trig 1 & 2 so that means you have a wiring issue.  It wasnt like that before so you have possibly swapped the positive and shield instead of + & - or something.  

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So you believe I have the positive and shield swapped now, I will double check. Should the Cam sensor should be a square wave and the Crank sensor have the "S" shape? How would the crank signal effect the cam signal? Is there anything else I can check? 

Thanks!  

 

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On 8/19/2021 at 9:26 AM, S4-VR6 said:

So you believe I have the positive and shield swapped now,

No, that is just one possibility. Cross talk generally means you are missing one of the common connections back to the ecu.  You need to research the proper pinout for your sensors and confirm you have continuity from the correct ECU pins to the correct sensor pins.

 

On 8/19/2021 at 9:26 AM, S4-VR6 said:

Should the Cam sensor should be a square wave and the Crank sensor have the "S" shape? How would the crank signal effect the cam signal?

Yes.  So the fact you can see the shape of the crank signal in the cam trace means you have current from the crank sensor passing through the cam sensor wiring.  It would suggest one of the common paths is missing.

 

So for example instead of something like this correct wiring:

982GlGA.png

 

You have ended up with something like this.  The common ground connection to the ecu is missing so the only path for the crank signal to get back to the ecu is through the cam sensor:

B6boVSr.png

Note these schematics are just to show effectively what is going on electrically.  In real life the actual problem may not be at the ecu end like I have drawn but could be caused at either end with as I mentioned earlier a shield connected to the wrong pin or something.

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In plug A there is a shield ground and a sensor ground and those need to be wired as such correct? i.e. my shield from the crank sensor to the shield pin and my      -ev to sensor ground pin? The cam sensor has no shield so ground it to sensor ground not shield ground. The cam sensor is a Hall sensor and the VW wiring diagram shows it wired to 12vdc. I did not realize this and wired it to the +8V pin (which only measured at 4.6V with the key on), do you anticipate this being an issue? My MAP is currently wired to sensor ground, is it ok for all three of these to share this pin? 

The reluctor wiring diagram in the manual shows the shield and -ve tied together for a reluctor which would make it impossible for me to reverse the crank sensor polarity without putting in the sensor into the ground circuit and hence create cross-talk, at least that is how I am interpreting it.  (pg 29 of the manual).  

I rolled the wires back but do not have the scope to test today but I am not expecting any different results than the first waveform I sent because i have now returned it back to the original wiring. 

In your first diagram above I am sure you meant to tie the -ve's together and not have the sensors in series? 

Thanks!

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1 hour ago, S4-VR6 said:

In your first diagram above I am sure you meant to tie the -ve's together and not have the sensors in series? 

Oops, I did have the +/- wrong on the cam sensor which made it look a bit odd, corrected that now.  

 

1 hour ago, S4-VR6 said:

In plug A there is a shield ground and a sensor ground and those need to be wired as such correct? i.e. my shield from the crank sensor to the shield pin and my      -ev to sensor ground pin? The cam sensor has no shield so ground it to sensor ground not shield ground. The cam sensor is a Hall sensor and the VW wiring diagram shows it wired to 12vdc. I did not realize this and wired it to the +8V pin (which only measured at 4.6V with the key on), do you anticipate this being an issue? My MAP is currently wired to sensor ground, is it ok for all three of these to share this pin? 

The Shield/Gnd and the "Gnd Out" pins are all sensor ground, they can be used interchangably.  In our looms with have both trigger sensor grounds and the shields for both triggers all spliced to pin A7.  But they dont specifically need to be, as long as all shields and all trigger grounds are connect to any of the sensor ground pins is fine.  8V should be fine for the cam sensor.  

 

1 hour ago, S4-VR6 said:

The reluctor wiring diagram in the manual shows the shield and -ve tied together for a reluctor which would make it impossible for me to reverse the crank sensor polarity without putting in the sensor into the ground circuit and hence create cross-talk, at least that is how I am interpreting it.  (pg 29 of the manual). 

No, it works fine, the sensor generates an AC signal.  Neither the + or - pin on the sensor would have continuity to ground normally.  As long as you swap the correct pins at the sensor end and not the ecu end.  What is the part number for your crank sensor?

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