Originally Posted by
Predator
I'm getting 9 MPG in the city no matter the driving style. I really think there's something that is causing this, maybe you guys can help.
To give you some background about the car, it's a 2007 Crossfire Limited Automatic NA.
New air filters, new sparkplugs, new fuel filter.
The mass airflow sensor got cleaned.
New tires, wheel alignment, etc.
Everything seems fine, the car behaves normal.
From all the research I did, what's left would be the injectors or the oxygen sensor, I didn't change those.
Let me know what you guys think and if you experieced something like this.
THis just barely makes sense. If I drive the SE the hardest I can, thru the Dragon and other roads all day, I get, at the very lowest, around 12-13. I know this cause I refill every day when I'm up there.
If you drive it reasonably, I"d expect 20-22 in town, I know I get about that (hard to say cause I mix town/country driving so much and I usually get around 25).
How could the car be running THAT rich and not show signs of rough idle and lowered performance (that is, lower acceleration, etc.) with that much more fuel going into the engine.
What is the fuel pressure like? I would never proceed too far with a fuel system / fuel consumption issue without knowing the fuel pressure. The ECU assumes 55-60psi. But there is no sensor telling the ECU what the pressure is, it simply opens the injectors for the amount of time that would be correct, based on correct fuel pressure. With low or high pressure, you will get lower or higher fuel/air ratios. Therefore, if you do not know the fuel pressure, you don't know what the engine is getting, the O2 sensors only measure the amount of oxygen in the exhaust, not the amount of unburnt fuel, nor any direct measure of other emissions in the tailpipe.
I've had two instances of incorrect fuel pressure in injected engines, the symptoms made no sense, until I put a pressure test kit on it, then suddenly I knew what I had - bad fuel pump/filter/regulator/fuel pickup.