Gas mileage disappeared
Thread Starter
11 Second Club
iTrader: (4)
Joined: Aug 2004
Posts: 1,832
Likes: 0
From: Rockland County, NY
Gas mileage disappeared I've been keeping track of my gas mileage and I would usually get around 20-22 combined city/highway, so I figure around 17-18 city. Just recently I've been getting 10-11 mostly city. I haven't changed anything on my car. What could cause this huge drop? It was with more than one tank of gas too.
Originally Posted by 02 Camaro SS
I've been keeping track of my gas mileage and I would usually get around 20-22 combined city/highway, so I figure around 17-18 city. Just recently I've been getting 10-11 mostly city. I haven't changed anything on my car. What could cause this huge drop? It was with more than one tank of gas too.
TECH Veteran
Joined: Dec 2001
Posts: 4,117
Likes: 0
From: Ft. Lauderdale, FL, USA
Originally Posted by 02 Camaro SS
I've been keeping track of my gas mileage and I would usually get around 20-22 combined city/highway, so I figure around 17-18 city. Just recently I've been getting 10-11 mostly city. I haven't changed anything on my car. What could cause this huge drop? It was with more than one tank of gas too.
If your PCM, for whatever reason, goes into a Speed Density tune you will burn alot more gas, ALOT. And you will get no codes that this has happened and the car will run PERFECTLY fine.
The way to see if you're in SD tune.....start the engine, while its idling, unplug the MAF and rev it up by the TB arm. If it runs normal you're in SD tune. Also, you can unplug the Throttle Position sensor too, and the engine will run normal without it if you're in SD tune.
My car right now, is in SD tune, did it on its own long ago....have no idea why...but my car/engine runs PERFECTLY. My gas mileage did get worse though.
.
Thread Starter
11 Second Club
iTrader: (4)
Joined: Aug 2004
Posts: 1,832
Likes: 0
From: Rockland County, NY
Originally Posted by _JB_
How old are the o2? Just because the SES light isn't on doesn't mean they are reading 100% I believe.
Trending Topics
Originally Posted by 02 Camaro SS
Over 4 years. Guessing that means they would be the culprits.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
TECH Veteran
Joined: Dec 2001
Posts: 4,117
Likes: 0
From: Ft. Lauderdale, FL, USA
Originally Posted by 02 Camaro SS
Over 4 years. Guessing that means they would be the culprits.
So, no, after 4 years they should be just fine unless you have some other problem that is damaging them.
Bad 02's will cause your engine to run like HELL, backfires, spitting, stalling, rich, missing....you will know something is really wrong.
A code will not always show from bad 02's, also a scan will not always show a bad 02, but an OBDII scanner will show you if they are working and switching properly.
Staging Lane
Joined: Feb 2007
Posts: 53
Likes: 0
From: Pensacola, FL
oddly enough, this just happened to me. I'd been running a little worse doing city/highway combined... I'd been getting around 18-20. Then my mileage spiked up for one tank, leveled off to normal for a tank, then plummeted to about 10.5 mpg. Unfortunately, I believe mine is attributed to strictly short city drives with no highway miles. However, I had a major exhaust leak for a while and I'm lookin at getting a cutout, so I may just invest in a good o2 while I'm at it. I'll let you know what I find.