Drop in mpg...

[TimelessClassic]

Hi,

I have an '03 G35 Coupe with 112k miles, well-maintained. I went to the Nissan dealership and they did the following:

1. Installed my k&n air filter
2. Mass Air Flow Clean

However, my mpg dropped about 15-20% as soon as this was done. Is it possible that the cleaning of the mass air flow somehow damaged the air flow sensor? Someone I know suggested that if the k&n filter is not installed properly and the debris around it is not vacuumed and cleaned, it will affect the air flow sensor.

The Nissan dealership (obviously) says mpg depends on my driving habits (really???) despite the fact that I keep telling them that my driving habits have remained exactly the same for the last 5 years.

Any suggestions? Thanks!

[audtatious]

I'm assuming they reset the ECU so the car will have to go through a relearning curve. Give it a while and see if the mpg comes back.

[TimelessClassic]

What's the ECU and why would they need to reset that?

[joe603]

ECU=Engine Control Unit

It baselines the fuel curves and "relearns" optimal settings.

[audtatious]

What's the ECU and why would they need to reset that?

I'm sure they reset the ECU or let reset due to battery disconnect when they cleaned your maf.

[TimelessClassic]

What's the ECU and why would they need to reset that?

I'm sure they reset the ECU or let reset due to battery disconnect when they cleaned your maf.

So what's the solution? Just let it be? I had been considering going back to an Infiniti air filter but if the ECU was reset, going back to an Infiniti filter won't fix it.

If I let it be, will mpg return to its previous levels? It's down about 20% now.

[TimelessClassic]

ECU=Engine Control Unit

It baselines the fuel curves and "relearns" optimal settings.

From k&n customer service:

"Since our filters flow more air than a stock filter, it will take a few tanks of gas for the computer to compensate for the additional air and learn the new fuel requirements of the engine. I would suggest running a few more tanks of fuel with a good mix of highway and city driving and see what it improves."