My car is getting just 100 miles per tank in city. When I had true dual exaust, I asked for a friend to make my closed loop temperarute to be 290 degrees, so basically my car never goes to closed loop. I bought and installed new heated O2 sensors, but my computer is ignoring them. And there is white smoke coming out of my exhaust all times. I have no cats and cc306, so maybe its normal? My oil lever and coolant lever haven't dropped in 1000 miles, so where is that white smoke comming? I read somewhere that unburned fuel looks black in exhaust, but maybe I am wrong.

Anybody lives close to Urbana Champaign, has programming software and could help me out . Mods got me broke, but now I almost cannot afford fuel to drive my car

 

Is this candid camera?????? Listen to what you just wrote. You somehow had the temperature raised at which point the PCM goes to closed loop. Why??????? Then you said you bought new O2's ??????? Why?????? When an engine is in open loop it will ignore the O2's you just bought and run on internal data tables and will run very rich.

Put the closed loop temperature back to 140 degrees. Get you a power programmer available everywhere and change the CL temperature.

Once you have it back to normal then see what is happening with other symptoms. White smoke is usually water. If you are the impatient type Do a leak down test. And also do a coolant system pressure test.

 

I am trying to get my open loop temperature to 140 ,but I don't know how. I do have a cable and a laptop. Doing a search now for how to do it. My car didn't leak any antifreezere in 1000 miles, and my coolant system stays pressurized even after a day of not running the car.

 

Stock lt1 on the city will give you around 140-160 depending on the kind of driver you are, on highways easily 210+. But a CC306 is a pretty big cam, and its normal to have SOME smoke come out your exhaust, as long as is not burned oil. The smoke could maybe be unburned gas, how rich is your car running?100 miles to the tank sounds kinda low, but its reasonable for a 306. what kind of gears do you have?

 

I have 3.73 gears. I want to get my car back to closed loop somehow. My car could be running rich. My fuel pressure is around 45 at idle due to 255 lb/hour fuel pump.

 

oh i see 3.73s, i guess thats why, 3.73s will give you a higher rpm, thats probably why. This is how far my limilted knowledge takes me, someone shed some more light here

 

373's won't kill your gas mileage like that. Actually they really won't affect your city mileage as you'll just be driving around in 5th instead of 4th if anything, but they'll take away from your highway mileage, but still nothing THAT drastic.

I'll say that your car is running rich because you are in open loop. You said you have a laptop and a wire, do you have the software that goes with it? I'd say download your car's PCM Program and poke around there looking for a setting that says "290" since you said that's what you told your friend to change it to and just adjust that to 140. Worse comes to worse you can have your friend fix it again?