I have a 2002 Maxima that came with an ECU upgrade. From what I read the ECU reprogramming dumps more gas into the cylinders. I'm getting 20 mpg on the Highway. I was hoping to do better. Does it make sense to have my ECU put back to OEM specs? If so can a dealer do this?

Thanks in advance

 

If you want better MPG, then definately go back to OEM specs. I was getting 26+mpg easily in my Max on the highway. I'm sure the dealer can take care of this.

 

What sort of ECU upgrade is this? I haven't of any that "dumps more gas into the cylinders". More details please.

 

Hard to say if a reprogram would help. More fuel does not mean more power, unless you are already lean. And at part throttle cruise in closed loop the computer will be adjusting off the O2 sensors for 14.7:1 Stoich., or optimal air/fuel ratio.

Now if you were to compare two programs at WOT then you could compare the mileage to the programming. Most "tuning" is done for performance, and most performance drivng is done at WOT.

One thing it could be with the programming is the timing advance at part throttle, more timing at part throttle will give you better mileage. With a scanner you can see part throttle timing, and if you know what the factory specs are from a stock programmed car, you may be able to simply adjust the base (idle) timing a liitle higher to make up the difference at part throttle cruise.

 

I didn't have the reprogramming done I just know that the former owner pulled the ecu and sent it out. He claims that it made a difference in HP's. I don't know but it is (or something is) killing my MPG. I do 75mph on the highway. I guess that doesn't help either. Do you guys think a dealer would be able to undo what has been done to the ecu/timing, etc?

 

This is true, but it depends on who tuned his ecu. They could have tuned the new A/F to go into effect @ 40% throttle. I'm sure the timing was advanced, but for the his engine, I'm sure they richen it up some, and maybe leaned in other places. . . once again depending on who tuned it.

If he didnt want to spend money at all, he could baby the throttle so he's in closed loop, but no one would drive like that.

Still for his sake, since he wants better gas milage than performance an un-tuned ecu would be better. I would suggest finding a used ECU, and installing that and sell your current one in the for sale section, I'm sure you could more than cover the cost of a used ECU for your car + change.

Dealer maybe able to undo what was done. If my memory serves me, the 03 ecu are RAM vs 4th gen which are ROM. Cost wise it maybe cheaper to find another ecu and sell the one you have.

 

Is it hard to get to the ECU? Would I have to take the dash apart?

 

its better to get it trade and make money of this