Hey Guys, so I'm now in the place of the car stumbling/bad idle/undriveable - long story - I switched to COPs last year it has an issue on longer gears (3/4) pulls into the higher RPM, it goes crazy/falls on it's face like it's hitting rev-limiter, etc. I was attempting to get a log of that issue while on track and when I hit it - the car went crazy and now doesn't idle or rev. To be clear, the car went from fine, but a minor issue in high RPM to barely running in a split second.
So the things I've checked:
Swapped the CAS to a different one - no change
Swapped in brand new plugs - no change
swapped to some stock injectors I had - no change
Flashed the tune and config onto a completely different mspnp2 - no change
I switched to the old non-COP coils - no change
checked the compression - dead even and very good across the board
Unplugged all the injectors/coils one by one - no change in how it idles/revs
Pulled the supercharge belt - just quieter, no change in bad idle.
I have a megasquirt log and the composite logger files here:
https://drive.google.com/drive/folders/1G1OE_9EITyThwx1vJW_OuibprS5WvGfi?usp=sharing
Here's a video of it running:
Plug gap? Could it be blowing out the spark? You said they were black...how black?
Yeah some new plugs could be worth a try just to rule that out...is it possible that the engine timing might've slipped somehow? I know that sometimes happens on 4AGEs (timing belt flaps around on decel so badly that it jumps a tooth) and has similar symptoms.
Belts don't jump on these - but it would be interesting to check the air gap on the crank sensor. Easy enough to do and a slightly-too-big gap would maybe do this.
Assuming the 1.6 has been updated with one. I'd be looking for signal dropouts in the logs anyhow.
^On my MS3X, when this happened it would cross a threshold for missed crank sensor pulses and throw an error code. If you don't have the threshold set, you could be getting this issue with no error code though. If it doesn't even idle then the problem is severe.
Along the crank sensor line - the wiring to the CAS can fatigue and become intermittent. A stock ECU will throw an error code for it, yours will not. A simple wiggle test can be revealing.
Thanks folks!
I've ordered new plugs, will get them put in shortly to test - it needed them anywho.
I've been suspicious of the CAS since it started, but because of my coolant re-route it's kinda a pain to remove and replace (I have a spare on hand). This car only has a CAS only, no crank sensor I believe (stock 1.6 setup + mspnp2).
I've been told that I can just check the highspeed logger and it will tell me if the CAS is bad/not reading correctly - but I'm not sure what that log is supposed to look like so I just dumped the data in the above google drive link hoping someone could tell me what's right/wrong. I don't have a running setup to check against.
If it's the CAS, it's a good chance it's the wiring that comes out of it just a couple of inches downstream of the connector. That's usually accessible enough that you can grab it and wiggle it and see if anything changes. There are two signals coming from the CAS. It's one of those low effort checks that may not be the problem but it's so easy to do that you pretty much have to.
Stock 1.6 is all CAS, no crank.
I'd be checking your grounds as well. A weak ground that has become worse can have weird effects. I had a problem with a Miata once where a ground wire was too short, and every time the engine rocked over it would disconnect and kill the ECU, then the engine would rock back and it would wake up again. It had that "cuts out at high RPM" feel. The tach dropping to zero while the engine was still turning was the key to that diagnosis.
In reply to Keith Tanner :
Copy that! Will give it a go and report back. Thank you!
Looking at the data log, I don't see any sign of a problem with the CAS. This would show up with the RPM dropping out and Lost Sync Count increasing. The log appears to only show the engine cold; do you have one of it fully warmed up I can use to take the warmup part out of the picture? Also, can you post a copy of the tune?
In reply to MadScientistMatt :
Hey Matt! Thanks for taking a look (and for the info, good to know for the future) - I've added the tune to the google-drive link (zipped up project directory).
I'll get a warmed up log this evening!
https://drive.google.com/drive/folders/1G1OE_9EITyThwx1vJW_OuibprS5WvGfi?usp=sharing
Fuel pressure and delivery, if it ran before and it still runs now at least most of the sensors must be in range. Went through headache like this before only to find plug filters or hidden filters that were plugged up causing it to run out of fuel on pulls.
In reply to wearymicrobe :
Copy that, I'll check my filters and pressure!
In reply to MadScientistMatt :
Hey Matt, added a warmed up log to the directory. I also changed to brand new plugs - the car seems to be running horrifically rich?
https://drive.google.com/file/d/1o0V31hq15uD811hmWSbJ7z1yq3tnL3no/view?usp=sharing
Checked both fuel filters and they are spotless, but I don't have the gauge to check fuel pressure right now.
boy, not sure what's wrong here...
For E36 M3s and giggles I swapped the CAS as well, no change. The grounds look ok, but I'm not precisely sure how to test. Wiggle test didn't effect the running.
The tune is pretty ugly, but if it ran OK on it... fueling around idle changes a lot of VE and it is bouncing around which won't help. It runs pretty rich all over.
Crank to cam timing good? Ignition timing still synced?
No lost sync in the warm log at all.
MAT moves around oddly as well, like there is noise. I would check grounds in the harness, from block to battery, etc.
This have 550cc injectors, fuel pressure 3 bar?
It's possible some fresh plugs and a quick tune will help clear up the idle but there could be another issue at high rpm that's completely unrelated.
In reply to Paul_VR6 (Forum Supporter) :
Thanks for taking a look! The setup - as is - has been running for a while, something broke while attempting to get a log with the new COPs (the only major change). I went from running and idling fine to broken in a split second. When the RPM went weird for a moment on the last pull something broke - though what, is the question. I've updated the check list at the top, plugs have been swapped.
I'll try and dig out some before logs, this car has always had a pretty rough and tumble setup and tune, but it'd help to be able to compare it to when it was running ok-ish....
So the usual rule of thumb is "it's whatever you touched last". When you did the COP conversion did you have to do any rewiring? If you've got an intermittent connection in there somewhere that could explain it.
In reply to codrus (Forum Supporter) :
No wiring changes, it was plug and play, and when I say "just did it" I mean, did it end of last year found the stumble issue and didn't really drive the car on track. It drove really well outside of high RPM/high gear. I couldn't replicate on the street without breaking the law by a margin so I was getting a log at a club day (or trying to) when I went from the car idles great and pulls fine to "we broken"
Plug swap and its pig rich? At idle or under load? Or both?
Are all plugs pig rich or only a few or just one?
Could it be too much fuel pressure?
You don't have a log of the session when the issue happened?
Thinking about it overnight, checking fuel pressure and just doing some basic idle tuning and a new set of plugs would be my first step.
That's warmed up? The ECU "thinks" you're at 135 degrees. You may have the coolant temperature sensor calibration off and have it think you're still warming up.
In reply to Paul_VR6 (Forum Supporter) :
Yes sir, plugs are swapped and I've been down the hole of checking the fuel, but don't have a gauge for the fuel pressure yet, working on that.
