Gas Mileage Down?
Thread Starter
Le Mans Master
Joined: May 2006
Posts: 6,774
Likes: 363
From: Midland TX
Gas Mileage Down?
I have a 2001 LS1. Up until last November at 40,000 miles I had been averaging about 18MPG or better in the city per tank.
In November last year I had a starter break off a chunk of the engine block, so the dealership installed a new short block. Since then I have about 1,200 miles on this new engine and I am only getting about 14 MPG. The engine runs great - smooth acceleration, plenty of power and idles smooth.
Any ideas why my MPG has dropped?
In November last year I had a starter break off a chunk of the engine block, so the dealership installed a new short block. Since then I have about 1,200 miles on this new engine and I am only getting about 14 MPG. The engine runs great - smooth acceleration, plenty of power and idles smooth.
Any ideas why my MPG has dropped?
Tech Contributor
Joined: Dec 2006
Posts: 10,962
Likes: 29
From: Van Buren Arkansas
Wounded Warrior Escort '11
Have you pulled your codes yet? I'm sort of thinking they forgot to hook up something. Any other problems...such as HVAC problems inside, therefore the small vacuum line on the rear of the intake might being disconnected. PCV valve tube having a hole in it? Plug wires not damaged and plugged all the way on? MAF clean? You may need to take it to a tuner to find out what's going on in the computer too...
Race Director
Joined: Mar 2000
Posts: 17,602
Likes: 20
From: Palm City Florida
I have a 2001 LS1. Up until last November at 40,000 miles I had been averaging about 18MPG or better in the city per tank.
In November last year I had a starter break off a chunk of the engine block, so the dealership installed a new short block. Since then I have about 1,200 miles on this new engine and I am only getting about 14 MPG. The engine runs great - smooth acceleration, plenty of power and idles smooth.
Any ideas why my MPG has dropped?
In November last year I had a starter break off a chunk of the engine block, so the dealership installed a new short block. Since then I have about 1,200 miles on this new engine and I am only getting about 14 MPG. The engine runs great - smooth acceleration, plenty of power and idles smooth.
Any ideas why my MPG has dropped?
One you are still breaking in the motor..
Two, I bet your O2's are getting lazy.. They dont always set a CEL when Lazy.. The CATS can eliminate a lot of the Hydrocarbons before the CEL ever gets set.. They are Cheap.. Change them.
Also
Clean the MAF too. But that almost NEVER has to do with Poor Gas Mileage.. usually poor performance.. when the MAF is Dirty.. it does not read the airflow correctly.. and in most cases reads too low.. which commands too little fuel, which makes the car feel like it's loaded with bricks..
Last edited by chuckster; May 12, 2009 at 10:23 AM.
Thread Starter
Le Mans Master
Joined: May 2006
Posts: 6,774
Likes: 363
From: Midland TX
My opinion 2 things are going on...
One you are still breaking in the motor..
Two, I bet your O2's are getting lazy.. They dont always set a CEL when Lazy.. The CATS can eliminate a lot of the Hydrocarbons before the CEL ever gets set.. They are Cheap.. Change them.
Also
Clean the MAF too. But that almost NEVER has to do with Poor Gas Mileage.. usually poor performance.. when the MAF is Dirty.. it does not read the airflow correctly.. and in most cases reads too low.. which commands too little fuel, which makes the car feel like it's loaded with bricks..
One you are still breaking in the motor..
Two, I bet your O2's are getting lazy.. They dont always set a CEL when Lazy.. The CATS can eliminate a lot of the Hydrocarbons before the CEL ever gets set.. They are Cheap.. Change them.
Also
Clean the MAF too. But that almost NEVER has to do with Poor Gas Mileage.. usually poor performance.. when the MAF is Dirty.. it does not read the airflow correctly.. and in most cases reads too low.. which commands too little fuel, which makes the car feel like it's loaded with bricks..
Have you pulled your codes yet? I'm sort of thinking they forgot to hook up something. Any other problems...such as HVAC problems inside, therefore the small vacuum line on the rear of the intake might being disconnected. PCV valve tube having a hole in it? Plug wires not damaged and plugged all the way on? MAF clean? You may need to take it to a tuner to find out what's going on in the computer too...
No codes and engine is running too smooth for there to be a vacuum leak I think. New plugs and GM Performance wires.
Last edited by Choreo; May 12, 2009 at 08:33 PM.
