When i first noticed a problem with gas mileage i went to the auto parts store and asked what it could be. They said the O2 sensor so I picked one up and installed it but the check engine light still came up. so I took it to my friends house and his Uncle came over, and he did a Code? check or something and it came up as a 23, so we then go through and check all the connections for emmissions and find a loose connection. so we plug that in and the "Check engine" light goes off. Now my car after we plugged that in idles crappy so he tunes the Carburator and in the proccess we find a Vaccum leak. My question is would this vaccum leak cause crappy gas mileage? BTW when this started i was getting 8.2 MPG now I get 11.5, where as i used to get 18-20. I have a L69 engine with no mods, in a 83 Berlinetta just so you know.

 

You may have had a vaccum leak causing the engine to run lean. I ve never heard of an L69 getting 20 mpg.

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"Real Men Flush 5.0's"

My RS

 

I had a vacuum hose that I bumbed and disconected and that caused my car to idle horribly (well maybe not that bad). At that same time i was doing mileage calculations for a few weeks afterwards. When I got tired of the sloppy idle I went and inspected everything under the hood and found the disconnected vaccum hose (that went over the driver side valve cover to the charcoal cannister) and connected it. I lost 1 MPG by connecting that one little hose.

go figure.

James

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1985 Z-28 305 TPI
215,000 mi. Original Eng.