Before moving to college I was 3500 ft. and had changed my MAF tables to add more fuel cause the BLMs were higher than 128 when I enter PE. Now I am at almost sea level and the car is running leaner again (BLMs are around 145 most of the time).

Is it running leaner because of the altitude change or cause the PCM is compensating for something? I don't want to change my MAF tables even more if the PCM will readjust itself a few days later.

Thanks

PS also at 3500 ft. I had to use 90 octane whereas now I can get 93, if that matters. Either way I wasn't getting much retard.

 

I have no way of even gueesing what else may be going on, but there is large difference in average air density between sea level and 3,500ft. And you are correct, it will run leaner. For low load/cruising I'd recommend using a stock MAF table and letting the computer compensate. Save your tuning for WOT.

Rich Krause

 

There are multiple things that can cause your lean condition: Fuel, air density, humidity.

Fuel you ask? Yes different gasolines have a different capability to produce heat, thus power per unit. How old is the gas in your tank? Could be a factor.

Our MAF's cannot determine humidity only what it perceives as a metered amount of air (water vapor included). This is why with my car, I can calibrate my MAF one day and be off by 4-5 BLM's (generally at idle) the next.

Something to consider, but don't worry so much about it.

Ben