Bad gas mileage help

**WarStryker13** · 04-13-2017

My 04 has a "door", behind the rear seat, under all the trunk carpeting. It's almost directly in front of the spare tire well, but it's got 8 bolts holding it down and appears to be tack welded... unless the factory installed it with sealant goop BEFORE painting the body... lol

**PontiacGrandPrix2005** · 04-13-2017

K thanks ill rip the car seat out later and have a look when the sun comes out if i get bad fuel pressure.

**PontiacGrandPrix2005** · 04-13-2017

Does anybody know what the maf readings should be at idle and throttle. My app has g/s

**Scottydoggs** · 04-13-2017

maf wont tell you any thing. watch the long term fuel trims.

**WarStryker13** · 04-13-2017

Maf is just for the PCM so it can keep the air-fuel ratio.

**Slick2500** · 04-13-2017

How's the downstream o2?

**PontiacGrandPrix2005** · 04-13-2017

Well long term is 15ish negative at cruise and negative 7 at throttle.

Short term bounces from plus 5 to neg 5

**PontiacGrandPrix2005** · 04-13-2017

The down stream o2 ...check the volts?
The up o2 sensor 1 is bouncing from 0.065 to 700ish
The o2 sensor 2 is holding at 0.680 to 0.700

**Slick2500** · 04-13-2017

Have you checked for vacuum leaks? It's kind of odd that your LTFT are so out of wack and no cel.
And how old is the rear o2 I mean, if it is as old as the front one you never know. And to be honest I have no idea if that is normal readings for o2 sensors.

**PontiacGrandPrix2005** · 04-13-2017

Thats kinda what ive been think maybe a vac leak....which should i spray around all the lines and any where else like hidden spots i should try and spray....carb cleaner i think right

**PontiacGrandPrix2005** · 04-13-2017

I have also noticed a rumbling idle ..kinda shakes the car lightly... And when i start AND shut off the car it feels like a rumble shake as well

**Slick2500** · 04-13-2017

Yup carb cleaner.

Sent from my SAMSUNG-SM-G870A using Tapatalk

**PontiacGrandPrix2005** · 04-14-2017

All i had was maf cleaner. Didnt notice any changes with the idle. The app has a vac pressure widget. Would i get a good reading from that? If so what should it be. Or the fuel pressure gages at the auto store does fuel and vacume i belive.
This is driving me crazy and killing my wallet. I watched pretty much a quarter tank go in two days only driving 25-30 kms

**PontiacGrandPrix2005** · 04-14-2017

On the emmissions test on the torque app it says its all good except the evaporative system incomplete ?related

**Scottydoggs** · 04-14-2017

evap can take forever to be "ready" gas level needs to drop past 1/2 a tank or some bs as part of its test.

**PontiacGrandPrix2005** · 04-14-2017

That sucks, i thought i was on to something

**tc300** · 04-15-2017

i cleaned out my fuel tank in 11' and have put a new fuel filter (wix) on twice since... instantly noticed a difference!!
00" GT stock, still get 20mpg ish in town driving

**PontiacGrandPrix2005** · 04-15-2017

Im not to sure im gunna drop the tank out just yet. I want to order this tester for fuel and vacume. Would this one work OTC 5613 ...on amazon.com. But it only says low fuel pressure on the fuel side of it.
I have this feeling that everytime i start the car ive watched it drop. Does it check high fuel pressure? Or im i sniffing glue sticks.....
And does anybody think that the rumbly starts and some what shaky idles have anything to do with the fuel being eaten up. Also the rumbly shaky when i turn the car off.