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DIC MPG flucturating

smitz327

smitz327

New member
I have a 2000 GT and the MPG fluctuates badly, Just filled it up the other day and maybe driven it maybe 20 miles city and already an 1/8 of a tank is gone. Getting like 8 to 10 miles to gallon from what it says; it has never been very accurate. On the highway when I open it up to say 70 MPH, the MPG stabilizes to around 25 MPG and maybe 340 to the highway on a tank. I have a cold air intake in it also. I also smell oil and gas while sitting at a light or when I back the car in to garage. The car runs very good and smooth it seems, no hiccups or sputtering.
 


If it smells like oil and gas it is probably leaking somewhere. Check the fuel lines and LIM gasket.
 
25 on the highway is at least a good sign. Being that you are in Illinois and it is winter would cause city driving averages to go to hell. Idling,warming car up, sitting at lights longer, tires spinning in the snow,etc makes my car go into the 10mpg range in a heartbeat. The MPGs sound normal this time of year, especially in snow states.
As far as that smell, I would hope you have done some visual inspections.
 


The DIC is not very accurate. Also sitting in city traffic with stop lights will kill gas mileage. The gauge isn't super accurate either. I can be driving and it won't move off of full, then all of a sudden it is down to 3/4 tank.

Use mileage driven divided by fuel used to figure out actual mpg.
 
If you're not checking your mileage vs fuel-up, you can't be sure if there's a problem at all. '97-'03 PCM does bad math on fuel.
 
I think you are right, probably going to drop it off at GM. I am wandering maybe that cold air intake is causing all the problems. It gets good gas mileage highway but bad local driving. I am usually easy on the peddle
 
One thing I did try is take the MAS out to check it and make sure it is clean, no problems found, looks clean
 


I took your advice and cleaned the MAS with contact cleaner that is safe for plastic and blew it dry. Not sure if it is to early to tell but I took it down to the store and noticed a huge difference on the DIC and after resetting it, it averaged around 20 MPG. I understand it is not accurate but before it was reading 12 or lower. I will keep the thread updated.
 
Update! ran the tank of gas out and got just under 200 miles to the tank full and that is from the mileage on the gage cluster. Not very good for $45 dollars worth of gas
 
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