[crazy4c409]

So my vette has left me clueless. I was getting 18 in town and almost 21 on the highway not too terribly bad but not great. Since then the gas milage has gone down to 13-14 in town and 15 on the highway. I went to autozone and had the computer scanned no codes. No lights, tire pressure is good, already did a new fuel oil and air filter. Checked the plugs (they were a charoal grey type color but still really clean and only 30k miles on em) so Im thinking 02 sensor but wouldnt that throw a code? please help thanks guys!

 

[hoopty]

I would look for any thing that could let unmetered air into your engine. Leaking vacuum lines, bad PCV, anything at all. I had a Jeep grand cherokee that got 17 mpg until I was towing a trailer then it would drop to 4.9 to 5.1 MPG turned it had a vacuum leak under more engine load and was pulling unmetered air into the engine the computer added fuel to make up for the extra air and the end result was very bad mileage when towing. I don't know if you have the same type problem but it is something to consider good luck.:thumbsup:

 

[Joe B]

So my vette has left me clueless. I was getting 18 in town and almost 21 on the highway not too terribly bad but not great. Since then the gas milage has gone down to 13-14 in town and 15 on the highway. I went to autozone and had the computer scanned no codes. No lights, tire pressure is good, already did a new fuel oil and air filter. Checked the plugs (they were a charoal grey type color but still really clean and only 30k miles on em) so Im thinking 02 sensor but wouldnt that throw a code? please help thanks guys!

(In addition to Hoopty's good advice) It could "easily" be an 02 sensor without ANY codes being thrown(this is pretty common with a slow OR only "slightly" malfunctioning sensor).....if you do replace them, go with the AC Delco units(stay away from Bosch)......most high end tuners will agree that the Bosch units are hit or miss, and I've found this to be the case as well.......(if applicable) you may also want to give your MAF meter's resistors a good cleaning with "designated" MAF cleaner or if you can't find that locally...some rubbing alcohol poured onto the resistors or lightly dabed on with a well saturated Q-tip works good....just be VERY gentle not to hurt them.......and I would also throw a new set of plugs in for the heck of it....many of the High Mileage (IE:100,000 plus) rated plugs show signs of breaking down WAY before that time frame........Joe:thumbsup:

 

[RRT vette]

Good advice so far. I would also add to check the injector ohms and fuel pressure leak down numbers.