Need help from smart people

**Skinny** · 02-12-2006, 02:47 PM

I use my slightly modified 2001 SS as a weekend/nice day car. I drive a '99 Isuzu Trooper for my daily driver. My damn Trooper gets the worst gas mileage I have ever heard of for a mid sized SUV. 13 in the city and barely 16/17 on the highway. I removed the air box and added a high flow filter but all that did was make it loud. I thought I read somewhere that the O2 sensors really mess with the gas mileage because they normally don't work very well.
1. Any truth to that?
2. Do you think it would help if I were to put O2 simulators on to send the correct signal to the computer all the time?

And yes, I know you don't buy an SUV for the gas mileage. But, 15 in the city and 20 on the highway isn't too much to ask.

Thanks
Skinny

**02z28ls1** · 02-12-2006, 03:50 PM

02 simulators are put behind where the cat. convertors were to fake the computer out into believing that the convertors are still there.You have to have the correct o2 sensors in place to have the engine run right. And a 4 wheel drive vehicle that weighs how much?6000 lbs maybe?Isn't going to get good gas mileage-20,no way. Most full size SUVs get more like 10-12 mpg,consider yourself lucky.That's why I can't understand why anyone would drive one of these on a daily basis-go figure.No I don't think you will improve on that very much.

**Skinny** · 02-12-2006, 04:53 PM

Yeah, I know where they go and I know what they do. I use them on my SS.

What I am wondering is if using a simulator would be better because it would send a consistant signal to the computer to run a certain fuel to air ratio rather than the sensor trying to read the moisture/air/fuel and whatever else they read? I can't believe that a o2 sensor sends an accurate reading to the computer.

Skinny

**hammertime** · 02-12-2006, 06:20 PM

Originally Posted by Skinny

Yeah, I know where they go and I know what they do. I use them on my SS.

What I am wondering is if using a simulator would be better because it would send a consistant signal to the computer to run a certain fuel to air ratio rather than the sensor trying to read the moisture/air/fuel and whatever else they read? I can't believe that a o2 sensor sends an accurate reading to the computer.

Skinny

The O2 sensor is actually very accurate at around 14.7:1. An O2 simulator serves a difference purpose it is sending a constant signal back to the PCM. The sensors before the converters read the actual A/F ratio, and feed it back to tell the computer to meter more/less fuel to maintain the correct ratio. In operation, the PCM basically cycles the engine from rich to lean immediately around the stoich ratio. A simulator would only send one constant signal back, and therefore break the feedback loop. More than likely, you'll get a check engine light as the PCM will probably see it as a dead sensor.

Outside of that, it definitely won't help your gas mileage.

**hammertime** · 02-12-2006, 06:41 PM

Actual ratings for a 99 Trooper are 15-16 city, 19 highway.
http://www.fueleconomy.gov/feg/sbs.htm

Keep in mind, cold weather, long warmups, aggressive tire treads and use of 4-wheel drive all will drop your mileage.

Best ways to increase you mileage:

Inflate tires properly, the more pressure in them, the less rolling resistance. If you have wider or taller tires than original equipment, consider changing them back.

Start your car up and go in the morning. Yes, its colder inside, but it will actually warm up faster (especially an automatic) when its driven. You get 0mpg idling in neutral.

Look at your driving habits, light acceleration saves a great deal over jack-rabbit starts. Light throttle lets an auto upshifter sooner to the next taller ratio. If it's a stick, try short shifting gears, even skipping one here and there when you don;t need to accelerate fast. The faster you spin the motor, the more air & fuel you suck in, no matter what the load.

Outside of that, a high mileage car can benefit from a good tune-up. New plugs, wires, air and fuel filtershelp get the most possible economy. And to go back to your O2 sensor question, they can deteriorate with age and accumulated miles too.

**Fastcar** · 02-12-2006, 06:55 PM

In addition to everything mentioned above, are you sure you don't have a clogged cat? Was your gas mileage better when you first got the Trooper? I had a clogged cat on my 4Runner and my mileage & engine power went to cr*p until I replaced the cat - the difference was like day and night, felt like I had a new engine. (I then also replaced the O2 sensors with the cat.) (Damned cat, never could figure out how it got up into the exhaust system... 8-P)