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This has happened twice now. So I'm driving to Atlanta, and right as I turn on 285 (loop around atl.), my WB starts reading full lean. If I mash the pedal it reads ~16-17. Should be reading 12.7. Both times were after roughly 45 minutes of highway driving (light constant throttle). The car drove completely normal, no hesitation/misfires, etc. I pulled off the highway and went into light city driving, and the WB reading started slowly dropping back down to normal. Any ideas what's causing this?
My hypothesis is either the sensor is getting cooked or the physical connection between the O2 signal/gauge wiring is getting too hot. No, I don't have datalogs, Atlanta traffic is crazy enough in a Miata.
The first time it happened I pulled off and dumped fuel across the whole map until the gauge was reading close enough to normal. After a short bit it was reading 10s, so I loaded the old fuel table up and it was completely fine again.
Sensor is a brand new AEM 30-4110. Ran on a pretty rich map for maybe 300 miles, now it's running on a very slightly rich map.
I have no clue. I'll get that tune uploaded tonight. Car is currently out getting a clutch job, and I'd need to set out a solid 2 hours to get a log, Might be able to next week.
Yes, you have the stupid air density table. So if your car gets incredibly heat soaked, 140 isn't unheard of, and by then it's pulling 12% fuel. I'm not saying that's the problem, but it's work a look. You're saying your WOT afr target is 12.7, so I'm guessing your naturally aspirated? That makes this more likely.
I actually picked it up tonight, RSpeed knocked out the clutch job super quick. I was pretty careful on the way home not to get intake temps too high. No issues with AFR. I'll change the table values and take it for a long drive on Friday to get some logs/work out the tune. Whenever it gets consistently warm will be the true test, it's only driven in 70*F max.
Here is the comparison between the EFI Base map and yours. As Curly mentioned your current tune is pulling 12% fuel @ 140f while its much less aggressive at only 0.9% with the base map. Probably something datalogs would help point you in the right direction to values that'll make more sense for your application. Good luck!
Correct, I've change the table to match the one DIYA suggests. Tomorrow is highway driving to try and provoke some problems, but it should be pretty good with the fixed baseline table.
Still waiting on an answer: Could I have done any damage to the engine?
Running lean certainly can, as lean conditions do cause higher temps resulting in higher potential of pre-detonation & knock due to pre-ignition events. Its hard for anyone to tell you 100% whether it did or did not do damage to your engine. There are some 'signs' if your engine is damaged based on higher than normal oil consumption or low oil pressures. Best way is to disassemble and do a visual inspection of the rods but that is wayyyy overkill if your car is running fine now and without perceivable knock (audible or in logs).
Pull the plugs and look for damage to the insulation around the central lead. No damage does not mean you are totally safe, but damage means you did have detonation that was strong enough to break the plugs. It is not definitive, but may help your peace of mind.
Changing the ADT probably worked? I wasn't able to get intake temps above 80*, but it should at least be much better if they get back up to 140*. Oil pressures are as normal, and I never heard any detonation/pinging when I was having the issue.
WB reads full lean after highway driving.
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