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Old 04-01-2009, 02:20 AM   #1
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Unhappy FM Link ECU A/F problems

Okay geniuses, see if you can tell me what's wrong here. I drive a used FM II turbo 94 miata with about 130,00 miles on it and two previous owners (so really, I should have foreseen a great deal of headaches anyway). I finally plugged a laptop into the link ecu, and I went through the whole song and dance of fine tuning the thing without the dyno. It took me a few hours, but I managed to do it. Anyhow, after all that super precise tuning, the A/F ratio is still way out of whack. The L3 autotune feature will sit pegged at its limits, trying to tune the thing as lean as it can, and then ten minutes later, it will start going the other way, trying to tune it as rich as it can. It's had this issue since I bought it, but I had optimistically suspected that it just needed fine tuning. I have two suspicions: either the WBO2 sensor is bad, or the 550cc injectors were installed poorly, and some kind of bad connection is throwing the fuel metering off somehow. I am completely open to any suggestions as to how I may find and solve the problem. Flyin miata tells me they think "something may be wrong with the way A/F is being measured." Not too much help there. Help me, miataturbo, you're my only hope.
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Old 04-01-2009, 04:54 AM   #2
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Which WBO2 are you using? Also, are you turning on L3+L4 after you are done tuning?

Is your fuel pump pressure okay? If its not able to maintain a constant pressure then that would effect how much fuel is being injected and the L3 value.
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Old 04-02-2009, 03:05 PM   #3
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I'm using flyin miata's WBO2 sensor with the AEM gauge. It's the one they supply with their kit. I turned on l3 after I was done tuning, but I left l4 off just because I didn't want it to interfere with my troubleshooting. The fuel changes are too large and too sudden for l4 to compensate, anyway.

As for fuel pressure, I don't have a way to measure it right now, so I couldn't say for sure. You guys know any tricks for checking fuel pressure?

I'll post a datalog soon, maybe that will shed some light.
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Old 04-02-2009, 03:20 PM   #4
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ok check your map readings because a bad map signal will throw fuel off. also how old is the O2 sensor,, my friends aem o2 went bad after 6 months of driving it with bad A/f reading. when is it showing bad a/f reading boost, no boost all the time? i have a link and i have dealt with a bunch of problems but now i am good at checking everything before i waste me money buying parts. tell me more about how the car acts and what is it doing. i have your same set up and so does my friend with both use aem wide band with gauge.
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