Terrible Gas Mileage

[drumking1721]

Originally Posted by Mike Jung

^
You are lucky you didn't have mis-fires, from lack of fuel flow

yea no ****.....i took it off and the end where it comes out,or goes to the engine...it came out on my arm and the gas was black and iw as like wtf........

Originally Posted by Mike Jung

^
Might of been a stuck open/failing thermostat.

If the engine does not get up to normal operating temps.
& runs cold.
It will run richer until it does.

With a stuck open thermostat:
The engine coolant goes to the rad to early (by not being closed) & cools the engine coolant down before it gets to the normal operating temps.
So it would take forever to get warmed-up to the normal operating temps.

Not necessarily, 12 to 25mpg is a HUGE jump.

Our CTS right now has a thermostat stuck open, it's throwing the P0128 (waiting for the weather to warm up to take it out, as you gotta remove the intake manifold to get at the t-stat on the 3.2L DOHC) Anyways, we're been getting the usual mileage since we bought the car, ~10L/100km and less.


As for restoring gas mileage it could be a billion and one things,
Fuel Filter like someone said,
Air Filter like someone said,
Plugs,
Plug wires,
FPR like someone said,
PCV,
O2.. etc

Just go for the cheap fixes for now, like air filters, PCV and see if it improves. I just did my Fuel filter & Plugs & wires today, hopefully I'll get back to the 500km a tank I used to get..

[pauljs75]

What's funny is considering the problems poor fuel flow can cause, that nobody has figured out a way to monitor fuel pressure as part of a diagnostic system. With all the stuff going to a computer, you think they'd have that by now. *shrug*

[drumking1721]

I need a fuel pressure gauge,i put that adjustable one in it and the gauge it came with broke on the fuel rail...so yea idk what the pressuure is right now

[gectek]

Originally Posted by pauljs75

What's funny is considering the problems poor fuel flow can cause, that nobody has figured out a way to monitor fuel pressure as part of a diagnostic system. With all the stuff going to a computer, you think they'd have that by now. *shrug*

it isnt that no one has done it, its just that gm didnt do it then. ford has a sensor for FP on their fuel rails, and the new PWM fuel pumps will use that as well. also if he had a t stat problem it would show up as a SES light with code P0128...did u find the cause for the bad MPG yet...and drumking did the new filter help you out any

[tenspeed]

Originally Posted by 20SilverGT00

Yeah, I have 130k on it. I have run techron injector and system cleaner on a regular basis, however, the fuel filter hasn't been changed in quite a while. I'll definitely do that. Thanks for the advice!

With 130K on it, your top O2 sensor is bad. That makes the car run on a open loop like when the engine is cold.