Notices
MEGAsquirt A place to collectively sort out this megasquirt gizmo

Yet another annoying misfire (?)

Old May 27, 2026 | 12:37 AM
  #1  
DuneBugDrew's Avatar
Thread Starter
Newb
 
Joined: Mar 2024
Posts: 6
Total Cats: 0
From: Eastern Iowa
Default Yet another annoying misfire (?)

Having a dumb issue I can't figure out.
My nb1/bp4w was running great, then developed a very inconsistent problem. Occasionally, under high boost, it will cut out for a split second. Sometimes for longer, almost like the key is rapidly being cycled on/off. I discovered that the RPM signal drops to, or near zero at these times. Attached is a very short log of it happening once.

I also have a composite log of it happening a separate time I will link to here: https://drive.google.com/drive/folders/1Qfua2N5VJoNFqzfRq9e7woXCTh69SOp3?usp=drive_link
I found a couple of brief instances where the cam pulses seemed to happen too far apart, while getting too many crank pulses-triggering the red sync error in MegaLogViewer. I'm new to reading that type of log.

Cam/crank sensors are both pretty new - Mitsubishi/Beck/Arnley, respectively. Tried a different cam sensor with the same result, and zip tied the connector to make sure it's not coming loose. Might try a different crank sensor, too, but don't want to go full parts cannon. I have extensively messed with trigger wheel gap. Brand new main relay, replaced because of a separate issue I had.

Really confused at just how sporadic and random it seems to be.
Seems to almost always happen in 4th, 5th, or 6th gear which makes no sense to me.

Running LS coils from FlowForce, they've been great other than having to replace plug wires recently.
Attached Files
File Type: mlg
2026-05-17_10.08.30.mlg (426.2 KB, 2 views)
Old May 27, 2026 | 12:45 AM
  #2  
Fireindc's Avatar
Elite Member
iTrader: (13)
 
Joined: Dec 2006
Posts: 7,739
Total Cats: 915
From: Taos, New mexico
Default

Hey bud. My nb1 motor setup developed a misfire shortly after getting the swap running. It started only in boost and got worse. For whatever reason switching the main trigger setup from rising edge to falling edge (or vice versa, I can't remember) fixed it. Be sure to re set your base timing after you make this change since it will be slightly off after.
Old May 27, 2026 | 12:52 AM
  #3  
DuneBugDrew's Avatar
Thread Starter
Newb
 
Joined: Mar 2024
Posts: 6
Total Cats: 0
From: Eastern Iowa
Default

Originally Posted by Fireindc
Hey bud. My nb1 motor setup developed a misfire shortly after getting the swap running. It started only in boost and got worse. For whatever reason switching the main trigger setup from rising edge to falling edge (or vice versa, I can't remember) fixed it. Be sure to re set your base timing after you make this change since it will be slightly off after.
Hmm, interesting. I'll check that out. Just weird that it's run flawlessly for 1k miles until this started inconsistently happening. Thanks for the insight
Old May 27, 2026 | 11:28 AM
  #4  
SimBa's Avatar
Elite Member
iTrader: (1)
 
Joined: Oct 2022
Posts: 1,922
Total Cats: 293
From: Idaho
Default




Definitely losing sync. Looks like a cam sensor issue based on googling the error code (lost sync reason 31). If you google that error code you should find some threads about how to troubleshoot and debug.
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
Saber008
MEGAsquirt
14
Mar 9, 2022 04:15 PM
FrankB
MEGAsquirt
11
Jul 27, 2020 03:05 PM
Morello
MEGAsquirt
13
Mar 6, 2019 01:40 PM
lyonnate23
MEGAsquirt
14
Feb 25, 2019 05:01 PM
DNMakinson
MEGAsquirt
52
Apr 26, 2017 01:58 PM


Thread Tools
Search this Thread

All times are GMT -4. The time now is 03:41 PM.