Turbo Miata cylinder 4 misfire
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.
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Have you done a compression test, Ethan? I think it would be a good place to start.
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Originally Posted by sixshooter
(Post 1561559)
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. |
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.
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Originally Posted by curly
(Post 1561565)
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.
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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...
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Originally Posted by Crumb
(Post 1561677)
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...
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Check coolant and ait sensors. If either one faulted to -40 degrees, it would cause the car to dump fuel.
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