Ethan636

So to start I have a 92 miata with a Cxracing turbo kit, 450cc rx7 injectors, walboro 255, and a adjustable fpr, running a megasquirt version 2 that has been dynotuned and ran great for about 3 days- now this was about a year ago and then it started misfiring which was very noticeable at idle but not easy to notice in higher rpms. I have replaced the plugs multiple times, tried a different set of wires- didn’t make a difference and I replaced the ignition coil. Nothing changed, checked that all the injectors are firing, but have not flow tested them. My afrs are pegged at a 10.0 just about the whole time I’m driving the car or idling, the misfire came out of nowhere, one day I just went to drive it and it was preset but the day before the car ran great. It has the same tune on it as it did then, I was going to begin checking all the grounds, but short of that I don’t know where to begin- any help would be appreciated.
thanks

sixshooter

iTrader: (12)

Have you done a compression test, Ethan? I think it would be a good place to start.

Don't be afraid to make an introductory thread in the "Meet and Greet" section.

Ethan636

yes I have, sorry I meant to say that I got +\- 160ish in each cylinder, but I retested cylinder 4 today and got 180

curly

iTrader: (25)

Yeah you can't expect a good idle at 10.0:1. Fix your AFR gauge, it'll misfire if too lean or too rich, or if timing isn't correct at idle, etc. Attach the MSQ and a datalog of it idling and "misfiring". Do this only once you've fixed the wideband.

Ethan636

so I talked to the guy that tunes my car for me and when I had this misfire problem before he leaned it out a bit for the time being, so it shouldn’t be at a 10.0 but I don’t have an idea of what’s causing that

Crumb

If the 'guy who tunes my car' sends you out with 10afr across the board, I would not go to him. You very well could just be power washing your cylinder walls and putting out the spark. Also not sure why he would tune your car IF your wideband clearly doesn't work either...

Ethan636

I have had the car previously tuned by the Same person, he did not send me off the dyno with my afrs at a 10, the car was tuned correctly and running as it should when I left- a week later something happened, that’s what I don’t know, and caused the car to run like crap and that is why my afrs are now pegged at 10. So that unknown issue is what I’m trying to solve

curly

iTrader: (25)

Check coolant and ait sensors. If either one faulted to -40 degrees, it would cause the car to dump fuel.