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-   -   91 Miata on MSPNP2 has random intermittent misfire (https://www.miataturbo.net/megasquirt-18/91-miata-mspnp2-has-random-intermittent-misfire-104784/)

John_B 03-04-2021 11:03 PM

91 Miata on MSPNP2 has random intermittent misfire
 
3 Attachment(s)
So I just got my car running on MS2, it has 640cc flowforce injectors, stock coil pack and ngk wires with some bk7re plugs gapped to 35 thousands.The car has a gt2560r on it and the MAP line is routed to the FPR. The tune is adjusted for the injectors and I am running the basemap tune as of now. I am trying to find out why my car is misfiring after driving it around for a few minutes. When I start the car it will idle fine and when I drive it around for the first few minutes it seems to run good. Once the car has been driving around for a while and I let it idle a misfire starts to occur. It will sound like its running on three cylinders and sometimes the car will shake and almost die. I have checked the timing of the ignition and the timing belt, both are correct. I replaced my spark plugs, coil pack and wires, yet the misfire still happens. I even ensured all injectors were connected right and switched them around to be sure. A compression check of my engine shows about 180 on all four cylinders and there seems to be no vacuum leaks. I provided my tune along with two datalogs, one being the start up where it idles fine and does not misifre "start up" and another being the datalog where the engine misfires "misfire badd". It is also good to note that my megasquirt had its fuel pump relay replaced under warranty a few months ago. I want to get a tune on my car but this misfire is preventing me from driving or getting a tune, If anyone could please help I would greatly appreciate it thank you.

SpartanSV 03-05-2021 12:01 PM

I believe your primary issue is a totally messed up VE table. This is not what a VE table should ever look like.

https://cimg2.ibsrv.net/gimg/www.mia...7b4c158cdf.png


Your startup log shows you idling at 16.5 AFR and it looks like you're using batch injection. If you setup your O2 sensor properly then you're running way to lean at idle. Your hot idle log shows even leaner but that may be from the misfiring. You're running open loop idle control which is resulting in about 700 rpm when the engine is warm. That's going to be to low without dialing everything else in.

Your ignition table is crap too. If that came from a basemap the dude who made it should be canned.

Fix your VE and add idle valve duty cycle. Then post the updated tune with a new log.


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