davwhite

Would like to improve fuel economy of my 2004 GS300
Can the ECM code be changed to burn a leaner mixture ?

Also can the Accessory lighting & radio be programmed to
stay on for 10 mins after ignition is turned off like most other cars?

captainva

iTrader: (1)

The ECU in these cars cannot be flashed so the only way to change your fuel mixture would be to run a piggy back or change to a standalone. At that point you'd be spending well over $1000 for the parts, labor, and a tune. Totally not worth it. Buy a different car if gas mileage is your primary goal

shwalker07

1. Not on a factory ecu alone. I have a 04 GS300 and it gets good mileage. You check the basic items:

- Air filter
- Spark plugs/wires
- Vacuum leaks
- Tire Pressure

2. You wan wire up a Miniature time on/off cycling delay relay and a main 12v relay somehow if you really want the radio to stay on.

What type of grade of gas do you use and also what MPG would you say you are getting?

Letsride

There is nothing to program to change that. You can rewire like Shy said......but not using the stock system!

Makdakas

1. Install a new air filter, its 7$ for piece
2. Replace spark plugs, if you don't remember when you did it. Use iridiums, they are expensive, but last longer
3. Take out your injectors and get them to injector service to check the flow and ultrasound clean them
4. Use a good quality 5w30 oil
5. Drive wisely in town, it's more economical for automatic cars to let them cruise. Pick up the speed and let off the trottle, when you need to speed up, add the speed with throttle and let off again. Plan far ahead and avoid unnecessary accelerating in town, where movement is "stop and go"

All this should give you 18-19 mpg around town, which is a good mpg for that type of car. You don't want to lean your air fuel ratio, it's unhealthy for your engine.
Or you can always mount LPG eqipment

captainva

iTrader: (1)

DO NOT use iridium. It says specifically in the manual to use double platinum on the GS300. The previous owner changed the plugs on my car less than 20k miles ago with iridum and now that I swapped to double platinum I have more low end torque and less vibration at idle. Use what the manual says and it will run better

Makdakas

Well, my user manual says use Denso SK20R-P11. These are iridiums... Are they really bad?

firelizard

iTrader: (1)

The cheapest way to improve performance and fuel economy of a GS300 is to sell it and buy a GS430.

MedicalDoc

Not too many 430s out there.
What about a Pontiac?