G4x M50 Plug-in Trigger sync issues during cranking

[Tye]

Hi everyone!

Been having a weird issue on my setup for a while. Every other time I try and start my car, it will crank extra long and produce a loud backfire out the exhaust! (Cops aren't very happy haha)

If i attempt to crank again, it usually starts right up and runs amazing once it does start!

 

Before anyone asks. Yes the timing is syncd, and yes all of ignition, ve, crank enrich, dwell tables are setup correctly! Car runs mint!

 

It seems like the coils are firing far away from TDC when this happens! I have not had a chance to get a trigger log, but I can get one if someone wants to take a look. 

I believe this issue has something to do with the new "Sync tooth" setting on the G4x's as the G4+'s don't have that setting and i've never had an issue with a G4+ Just a thought.

I'm using all of the M50 Basemap trigger settings (Other than the Trigger offset), which i have properly syncd on my car.

Curious why this new "Sync Tooth" setting was added. I was under the impression that the Cam sensor was in charge of Cam Sync on these ECUs

Also Id like to add that Ive had this same issue on other M50 Plug in G4x ECUs on Customer cars.

Any sort of help to resolving this issue would be great!

Thanks

[Adamw]

Sync tooth was fixed at tooth number 1 in G4+.  So if sync tooth is set to 1 in G4X the sync strategy is the same as G4+.  The sync tooth setting allows you to change the sync point if for example you have a VVT engine where the cam tooth moves across crank tooth #1.  

Give us a log of a few start attempts and a couple of trigger scopes.  

[e34WagonZilla]

Hello! I'm so happy I found this post.. I've been running a G4x e36x pnp ecu in my 1994 e34 for a few weeks and can't say I'm not pleased! Lately, I've been getting up early and starting the car at 4am every weekday for the past two weeks and cannot be having this misfire happening for another day longer. I need to fix this! I am also admitting I am the noobiest of the noobs when it comes to any engine tuning software, so keep that in mind please. Go easy on me, it's also my first post on this wonderful forum 

I'm also experiencing this exact same issue with the first attempt at start ending in misfire, followed by a successful 2nd attempt. I don't exactly know what to look for, based on some research and reading I've done in the last few days crank enrichment might have a lot to do with my problem. I doubt it's related to my cold start settings.

Since reading OP's post, I've looked into my triggers and noticed trig1 has two errors reported. I am unsure of what the  "Sync Tooth" setting falls under or where it's located in the software. During my first attempt at cranking the starter will turn the engine over endlessly and once i let off the ignition it's like a 12g shotgun is going off. I've also noticed this behavior being provoked after performing a store to the ECU and cranking, additionally when ambient temperature is around 70F and the engine is cool.

Some details about my specific situation:

1. I've been starting up my car every morning around 4am where the ambient temp is roughly 60F

2. I have a full custom exhausts with headers and no catalytic converter (as if my neighbors weren't bothered enough)

3. I am not currently running a wideband sensor

I have been messing around with idle control settings because I've always had a inconsistent idle but have since dialed it in for the most part; cold start is still rough and tends to bounce around when the car is running.

I'm adding in a G-drive folder with a single log and the tune I was running at the time. Please, anyone, take a quick look and let me know if there's anything awry (there is lol).

 

I will try and record some attempts at start (I only get one shot it seems) also will try and record a trigger scope even though I've never done that before.

https://drive.google.com/drive/folders/1PVE84n31nQNl11-On91urxBMCYR1ZzD4?usp=sharing

[Adamw]

Need to do a trigger scope and attach that and a copy of your tune.  

For the trigger scope go to ecu controls>trigger scope, crank the engine and hit the capture button, keep cranking for a couple of seconds.  Once the waveform has drawn on the scope screen, save it and attach here.  

[e34WagonZilla]

Even though it was warm this morning, I was able to catch the cranking misfire/backfire happen. The I captured the triggerscope while cranking, first attempt and did not start successfully. I attempted a start again and I believe I began recording a log during this. I'm not sure if you can record a triggerscope and a log at the same time and I was trying to start before attempting to crank since the ecu can lose power/connectivity to the laptop. Also, with triggerscopes, how do you view them in the software without being connected to the ecu? And do they only record a few ms of data?

https://drive.google.com/drive/folders/1caeh5D-18XS9PFjlvelzVMCgZSekaz4y?usp=sharing

Attached the same files below just incase something's wrong with the g-drive.

TriggerScopeLog-failedstartup.llgx idlestartup-triggerscope recorded.llgx M50b25TU-7BAR-600idle-igntune-idle.pclx

[Adamw]

Hmm, im not sure if this is a trigger issue, it looks like the engine kicked back while the trigger was all looking ok.  

Almost like it is too advanced.  Have you checked the base timing on this engine?  

[e34WagonZilla]

Using a timing light, correct? No I have not. All I know is I've never had this problem on the factory dme, and now having it with the g4x so I'm sure its the tune. Do you need more data? I can go get a timing light and mess around with that, I'm sure I'll need for the future anyways.

One thing I ought to try is take a step back and see if I'm having the same issues on the unmodified base tune.

Here is a triggerscope while the engine is idling during cold start, if that helps.

TriggerScopeLog-idle.llgx

It might be worth mentioning that adding a 2.0% offset to my dashpot under idle settings cured some severe undershoot problems I was facing initially. Maybe an indication that my timing is off? More backstory: engine is a lightly serviced (nothing beyond external service components) M50 at around 280k miles. Just trying to learn this platform in the meantime of building my M50B32 project.

[Adamw]

You need to check the base timing with a timing light before going any further.  

[e34WagonZilla]

Just ran out and bought one. I'll update you with my results soon.

[e34WagonZilla]

2 hours ago, Adamw said:

You need to check the base timing with a timing light before going any further.  

So what am I looking for exactly? I have my timing light clamped to my #6 ignition coil wire and am receiving a tach of ~600 and not sure what is really confirming that my base timing is okay other than that matching up with my idle on the software readout. It's an innova unit with a digital readout. I'm trying to research how to check the timing correctly.

[Vaughan]

find the tdc mark on the crank pulley, clamp light over cyl 1 ign lead, set timing in ECU to 0deg using the  Trigger -> Calibrate -> Set Base Timing window (remember to press enter after altering any of the values) and confirm that when the ECU is firing at 0deg that the timing light flashes at the tdc mark on the crank.

Basically confirming that the angle the ecu thinks it is at matches the angle the engine is at.

[e34WagonZilla]

1 hour ago, Vaughan said:

find the tdc mark on the crank pulley, clamp light over cyl 1 ign lead, set timing in ECU to 0deg using the  Trigger -> Calibrate -> Set Base Timing window (remember to press enter after altering any of the values) and confirm that when the ECU is firing at 0deg that the timing light flashes at the tdc mark on the crank.

Basically confirming that the angle the ecu thinks it is at matches the angle the engine is at.

okay. Sounds simple enough, I was almost on it. So I’ll need to remove the fan and shroud to view that timing mark, then I’ll get back to you guys with my findings. Likely tomorrow evening as I don’t have my special wrench with me. Thank you for the short and simple explanation.

I familiarized myself with the base timing config. I was messing around with the timing offset and tried to advance and retard the original offset by 10 degrees.
So starting at -328, I tried cranking at -318 and would not want to start, similar situation as when the motor is hesitant to start in the mornings but worse – sputters wheezes and dies, but no backfire. After trying -338 I found it would start okay but sluggish while under load.
Yeah I know I skipped verifying my timing, I figured -+ 10 degrees couldn’t hurt - plus I logged every attempt to look back at. Glad I know how to do trigger scopes as well, even though I don’t necessarily know what I’m looking at… lol

the more I mess with this engine, the more and more I think about how worn and beat it is and that it may not be the tune. There’s the entire timing system to blame because I’ve never serviced it, totally putting it off with my other motor in the scope. And of course 4 out of 6 of my cylinders are out of spec for compression readings sooo there’s that.

[e34WagonZilla]

Alright. So I got a chance to check my timing yesterday morning. Glad I did because it seemed to have fixed my issue (for the most part). 

here’s how I went about doing so:

- removed fan and shroud

- cleaned up my CPS as it was very grimy (could have affected drivability I’m sure)

- attached timing light to #1 cylinder coil wire

- observed the location of the TDC timing mark (dampener) in correlation to the mark on the timing cover. I had to paint my TDC mark on the dampener as I did not have one engraved in (reference other dampeners and marked ~5th tooth clockwise from missing tooth.

- timing was 2 degrees behind the mark after checking. I adjusted the base timing offset by (-)2 to account for this. My current offset value is -330, where it was -328 before.

- checked timing again; marks were lining up although there was slight inconsistency (my idle is set to 600rpm at operating temperature)

- reinstalled fan and shroud

 

So far, I’ve driven over 200 miles with the adjustment and the engine seems to be more tame in lower rpm load situations, idle is slightly improved, and when cranking this morning I did not experience a backfire or failure to start in multiple attempts. One issue that has become more prevailing as of the past week is low RPM misfires from 1000-3000rpm (maybe three or 4 instances during acceleration; 1 is too many). I’m going to pull my spark plugs and check their condition, as well as my coil packs. Otherwise it’s probably just time for a rebuild (I say this with for intentions of replacing this motor with a built one lol). I’m pretty sure the stock bremi coils are fairly weak and it’s been only 30-ish years sooo I’d say it’s a fair assumption there is weak spark. I guess I can test them with a multimeter. I’ll be using some Audi R8 V10 coils for the built motor; have them now can’t wait to use them.

 

[Adamw]

Hmm, thats odd, I dont think 2 degs extra advance would have caused the backfire, so you may still have an issue there.  

[e34WagonZilla]

I've been driving with the adjustments mentioned above since my last post on April 11th. Other than the lethargic driving experience, I've had significantly less occurrences of my cranking backfire.. Less. I've had it happen twice still. 

What are the chances this is a fault of my CPS? Would the triggerscope suggest this? I also would not be surprised if this is just a symptom of a very very tired M50TU, which it is.

[Adamw]

Your scope looks pretty good, I dont suspect the crank sensor at this stage.  

Actually I see you are on oldish firmware, it would be worth updating as there was a small change in the way some sync modes worked somewhere around 6.20.  Base timing needs to be checked again after updating from your existing 6.19.  6.22 is the current version.