Last post on Apr 20, 2008 at 9:14 PM
You are in the Chevrolet Suburban & Tahoe
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Chevrolet Suburban, SUV
#12 of 13 Re: 1999 Suburban dropping gas mileage suddenly with new engine [rodeoshoot
Apr 18, 2008 (7:24 am)
I had a similar thing happen 3 or 4 years ago with my 99 Suburban.
Noticed my gas mileage had dropped and my exhaust smelled as if the truck was running rich. I replaced the 2 oxygen sensors ahead of the catalytic converter (there are also 2 sensors located behind the convereter however those only monitor the converters operation) Anyway, the 2 forward oxygen sensors regulate the fuel air mixture and as they age they can cause the engine management system to allow more fuel than is necessary into the engine. After replacing the 2 sensors my city mileage went from 10 to 13. Before replacing those sensors I did ask my mechanic what he thought. His reply was not to do it because there was no code for the oxygen sensors stored in the engine computer. So if you have not replace your oxygen sensors recently you might want to try it. Good luck.
#13 of 13 Re: 1999 Suburban dropping gas mileage suddenly with new engine [rodeoshoot [remermn]
Apr 20, 2008 (9:14 pm)
I will give that a try. I will have my mechanic check to see if it smells to rich first. Chevy dealer told me the emissions was ok.
I was having some codes about the sensor before I had the right bank cat converter replaced about 40 days ago. I recently bought a chip and installled it and am still at 14 mpg on the highway. All the stations in this area are now selling 10% ethenal to us. So I guess the chip did make a slight difference since I was getting 13.5 on non-ethenal without the chip.