I'm not sure how else to describe this other than a 'drum beat' rhythmic misfire at idle. Its been consistent across multiple engines and I'm trying to determine what (if anything) in the megasquirt or tune could cause this. I've swapped the CAS, coils, plugs, wires... no change with anything. Car runs well when driving

In this video, the misfiring is amplified by the horrible transmission, when I push the clutch in (around 50 seconds) the mechanical 'pops' go away

 

Please post a datalog highlighting the section.

Have you verified that timing is correct with a timing light? If you lock timing, does it stay basically steady throughout the RPM range as verified with a light?

 

it does it all the time, here's a recent log attached, so any point where it's idling should be a good sample. Timing has been set and double checked, but I don't think i varied the RPM much while the light was on it, just held it a bit above idle

 

well that's wierd... looks like RPM lost sync there? I've never seen that before

 

I'm seeing a lot of little spikes in that log.

Several times the TPS seems to go to 100% with no associated change in RPM. This creates an AE event.

However without knowing what the car was doing, maybe that's valid.

Can you post a log of just the idle where the problem is happening? Also an ignition log?

Sync losses should show up in TunerStudio as an error. There is a counter.

 

Is there some documentation on capturing ignition logs? I assume it's the 'high speed loggers' tab, then 'tooth logger' and select 'capture to file' then 'start' ? I get a bunch of lines but I'm not sure how to read this

Attached a new log with just some idling

 

hopefully this is what you are looking for

 

How do you have your grounds set up?

 

ground are they way you guys suggested in my other thread: https://www.rx7club.com/megasquirt-f...ached-1088436/

 

I will take a look at these logs this evening.

Ken

 

OK, your log was a tooth log. What I need is a composite log. The tooth log just shows tooth times but doesn't let me see if or why it's losing sync.

That said, back to grounds:

Your TPS, CLT, and MAT sensors should all have their grounds going to the megasquirt sensor ground. The Megasquirt should be grounded to the engine where the stock ECU grounded, or directly to the battery - terminal. You should make sure that you connect all the grounds on the MS that you can to the ground point under the hood.

 

i may be missing something obvious... but the only options I see are 'tooth log' and 'trigger log'

 

forgot to respond to the second part of your post. right now all sensors ground to the megasquirt panel, and the megasquirt panel grounds to the engine. i'm not exactly sure where the stock ground point was, but I used a beefy spot on the center iron I believe right near where the oil filler neck goes. Should I separate the sensors from the panel ground and run them into the 'senor return' , which should be pin #7 according to http://www.diyautotune.com/images/ms...s/mswiring.png instead?

 

Yes pin 7, if you have a diyauto tune harness it is the black with white stripped wire.
The data log they're looking for is under the upper menu where File and Help are, I'm at work so i don't have tuner Studio in front of me so I'm not sure of the tab name. I Made the same mistake.
Ok I'm home now. The tab your looking for is the "Data Logging" tab. Works the same way as the other logs "start...name file...stop" and so on.

 

You should have one ground line for all your sensors that leads back to the DB37. Ultimately it joins internally with the MS ground plane but keeping them together on one line is a LOT better than grounding each individually. As mentioned, if you have the DIY harness, then there is a black/white wire specifically for this purpose.

 

Car is back on the road, back to troubleshooting!

Does anyone know why I woudn't have the composite log option?

In an effort to try everything possible to smooth out the idle, I swapped to the proper injector diffusers (had N/A ones in there before) and connected the air bleed line which was previously capped off. Also moved the megasquirt panel ground to the negative battery terninal.

Still have the rhythmic drumbeat idle misfire

 

did you try to change you ignition input capture.

 

i pulled all ignition advance from the cells at idle (went from +17/18 down to 0) and it's idling buttery smooth now.

 

Glad you got it fixed up. I'm going to update my map to decrease the timing at idle since for more stock ported engines that amount of timing isn't appropriate. I made that base map out of several I had and didn't change the idle timing from the map I started with, which I had made for a car with a fairly aggressive port and driver who likes an unusually high idle.