Sudden, drastic MPG drop
Thread Starter
Le Mans Master
Joined: May 2002
Posts: 5,930
Likes: 39
From: Still cruising the BVI in my head.
St. Jude Donor '08
Sudden, drastic MPG drop
I'm still trying to figure this out..,ever since I replaced the coupler and air bridge, I've dropped from about 22mpg around town to 11 with normal driving.
Several weeks ago I replaced both of those parts, and the drop happened immediately after combined with a code. I've since cleared the code, but the mpg hasn't changed. The only thing I can think of is the small airflow sensor that plugs ito the side of the air bridge- is there a forward and backward way of installing it, and maybe I have it in wrong? Other than that, I can't see any reason why this has happened.
Any ideas?
Several weeks ago I replaced both of those parts, and the drop happened immediately after combined with a code. I've since cleared the code, but the mpg hasn't changed. The only thing I can think of is the small airflow sensor that plugs ito the side of the air bridge- is there a forward and backward way of installing it, and maybe I have it in wrong? Other than that, I can't see any reason why this has happened.
Any ideas?
Racer
Joined: Dec 2001
Posts: 452
Likes: 2
From: Lynnfield MA
My guess is that the MPG drop is unrelated to the new parts.
What was the code you got?
The obvious test is reinstall the old parts and see if the problem
goes away. Maybe you'll find something disconnected along the
way.
For instance, you don't have the intake air sensor hanging loose
in the engine compartment where is sees hot air and has to add
a lot of unnecessary fuel?
What was the code you got?
The obvious test is reinstall the old parts and see if the problem
goes away. Maybe you'll find something disconnected along the
way.
For instance, you don't have the intake air sensor hanging loose
in the engine compartment where is sees hot air and has to add
a lot of unnecessary fuel?
Thread Starter
Le Mans Master
Joined: May 2002
Posts: 5,930
Likes: 39
From: Still cruising the BVI in my head.
St. Jude Donor '08
OK, here's a little more info- If I'm driving and I reset the MPG, it starts off in the low 20s. As soon as I come to a stop, it drops down abotu a tenth per second, maybe faster, until it hits about 10mpg (at idle???). Then when I move again it SLOOOWLY climbs back up to around 14 or so.
Don't remember the fault code, unfortunately.
Don't remember the fault code, unfortunately.
Melting Slicks
Joined: Aug 2003
Posts: 2,786
Likes: 7
From: Iowa
the drop at idle is normal. its a mpg calculator. at stop you are going 0 miles, and consuming some non-0 amount of fuel. 0/x = 0, there for at idle you are adding a lot more 0's to the average calculation. don't worry about that!
Racer
Joined: Dec 2001
Posts: 452
Likes: 2
From: Lynnfield MA
OK, here's a little more info- If I'm driving and I reset the MPG, it starts off in the low 20s. As soon as I come to a stop, it drops down abotu a tenth per second, maybe faster, until it hits about 10mpg (at idle???). Then when I move again it SLOOOWLY climbs back up to around 14 or so.
just a running average, and when you're stopped, each data point
is for some fuel used for no miles covered, so the average drops
pretty fast. What you want to do is get out on the highway, get
into 6th gear (or 4th gear for A4), and set the cruise control for
63mph. You should see something 27mpg or more for an MM6, and
maybe 25mpg for an A4.
Melting Slicks
Joined: Feb 2006
Posts: 3,400
Likes: 3
From: Sarasota Florida
What is your average MPG after a couple hundred miles of driving? Think about it, if you reset your MPG, put the car in neutral and took your foot off the gas pedal while coasting downhill your DIC could show that you are getting a 100 MPG if the hill was long enough.
Last edited by stormrider; Sep 27, 2007 at 01:51 PM.
Thread Starter
Le Mans Master
Joined: May 2002
Posts: 5,930
Likes: 39
From: Still cruising the BVI in my head.
St. Jude Donor '08
What is your average MPG after a couple hundred miles of driving? Think about it, if you reset your MPG, put the car in neutral and took your foot off the gas pedal while coasting downhill your DIC could show that you are getting a 100 MPG if the hill was long enough.Corvette Stories
The Best of Corvette for Corvette Enthusiasts
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
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
Safety Car
Joined: Jun 2007
Posts: 4,050
Likes: 1
From: Los Angeles CA
Did you have the battery unplugged at all? I recently had battery issues and had it unplugged. After clearing all codes and reconnecting the battery the MPG started over. I was driving home and checking it and was wondering why I went from 20mpg to 3mpg. I was sitting in heavy traffic and only went a couple miles. So every time you reset the MPG it starts over. If it was set a month ago then it takes all the driving in that month into it's MPG consideration. If the battery was unplugged and it resets the MPG then you are only going from the time you finished your mods. Drive it on the highway a bit and then check.
Burning Brakes
Joined: Jan 2003
Posts: 984
Likes: 0
From: New Smyrna Beach Fl
I see this quite a bit......owners will hit the "reset" button to clear a code. OK........now what are you doing to fix what the code was indicating??????? Clearing the code DOESN"T fix the problem.
Thread Starter
Le Mans Master
Joined: May 2002
Posts: 5,930
Likes: 39
From: Still cruising the BVI in my head.
St. Jude Donor '08
No, I cleared the code with that weird combination of buttons, got it from the forum. It worked, code is gone. Was hitting reset to clear the mpg snd see what's happening.
