Mileage gone way DOWN
Thread Starter
Pro
Joined: Jan 2011
Posts: 580
Likes: 8
From: Clemson SC
Mileage gone way DOWN
Recently noticed that my gas mileage has dramatically decreased, as in less than 1/2 what it has been being. I checked my fuel pressure and it shows a little low but engine still runs good. Wondered if low fuel pressure could be causing this by not working the fuel injectors right? Would this really make sense though or is it more likely that it is one or more of the fuel injectors? Or does anyone have other ideas that I can check out? BTW, I checked and no code errors. I am looking to figure out the problem and not just throw parts at it. Thanks!
Advanced
Joined: Sep 2016
Posts: 57
Likes: 3
Yea, but hey it could be something else! Just hope for the best. Could be something simple like a bad o2 sensor. It might be a good idea to check the cat anyways just for general maintenance and to see if it needs to be replaced or taken out.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Melting Slicks
Joined: Dec 2009
Posts: 2,234
Likes: 286
Is the engine running cool while going down the road? It should be at 190-200* on the road. If its running 180* or less you'll see it effect your mpg.
Your Maf sensor could be dirty too.
When you do the fuel pressure test, does it hold pressure after shut down?
Check all of the grounds, esp. the ones behind the heads. Those ground the ecm.
Your Maf sensor could be dirty too.
When you do the fuel pressure test, does it hold pressure after shut down?
Check all of the grounds, esp. the ones behind the heads. Those ground the ecm.
Thread Starter
Pro
Joined: Jan 2011
Posts: 580
Likes: 8
From: Clemson SC
Not sure how old the O2 sensors are so am thinking about replacing as part of maintenance anyway. Temps run around 200F so should not be that. The dropoff was pretty sudden so I am thinking it could be either sensors, MAF (but that should throw a code, I think) or Cat. Thanks for all of the suggestions. It will be a couple of weeks before I can get back to it as I just had a colon resection to hopefully prevent colon cancer. Quick aside: be sure to get your routine colonoscopy - could save your life or at least extend it significantly!
Thread Starter
Pro
Joined: Jan 2011
Posts: 580
Likes: 8
From: Clemson SC
Thanks, Jim. While laid up, I am trying to come up with a plan of attack to check out the possibilities with as much of a logical sequence as possible in order to avoid throwing parts at the problem.
Team Owner
Joined: Sep 2001
Posts: 62,153
Likes: 1,731
From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
Nice to see another Clemson guy.
If the engine runs good and there are no codes, and your mpg really sucks, suspect the oxygen sensor. Drivers' side exhaust manifold. It can fail long before it ever sets a code. There are O2 testers, and you can hook up the laptop and check its voltage readings to see how they oscillate, but that one is likely the problem.
Check the FP while running and after shutdown, that will point out an injector leak, but I'd bet on O2.
If the engine runs good and there are no codes, and your mpg really sucks, suspect the oxygen sensor. Drivers' side exhaust manifold. It can fail long before it ever sets a code. There are O2 testers, and you can hook up the laptop and check its voltage readings to see how they oscillate, but that one is likely the problem.
Check the FP while running and after shutdown, that will point out an injector leak, but I'd bet on O2.
Melting Slicks
Joined: Jul 2002
Posts: 2,223
Likes: 556
From: Tallahassee fl
could also be missing a couple of cylinders. The old GM computers did a very good job masking misfires. My brother drove a 1500 chevy truck for a couple years on 6 out of 8. when he found out and fixed it he was pretty blown away by the power.