Donohue96M6Z28

iTrader: (64)

As some of you know, I've been getting ~7mpg for the fast few months. I've been trying to get Lethal Performance to take a look at it, but it hasn't been easy trying to get them to check out my car. I called again tonight, and they said maybe a bad fuel sending unit? Does anyone know some of the symptoms of a bad fuel sending unit? Anyways I've changed the plugs/wires. I also had someone from AFB check it out a couple wks ago, and got a log. My drivers side 02 sensor was bad. I changed that, and he reset my fuel trim. I noticed a difference, and got 11mpg on that tank. I'm going to assume, that my mpg was decling during that tank though, bc now I'm back at ~7mpg. I kid you not, it appears as though when I shut my car off, and turn it back on. The level is always significantly lower. I think if I drive 20 miles without shutting the car off, I'll get WAY better mpg then if I were to shut the car off a couple times on the 20 mile trip. I've heard that starting the car uses a good amount of gas. But right now, it seems ridiculous. My tank was at a qtr...The needle hasn't budged while driving. But I have shut the car off/started it up 3-4 times. And now its at about 1/16 of a tank. I've had a few people check it out, I've "tried" to take it to Lethal to have them check it out again. They're supposed to give me a call tomorrow. I just don't know what to do...

retardedpenguin

iTrader: (2)

That sucks dude, my car does that too though. I will turn it off/on and it will go down like an 8th a tank. I don't get 8mpg though. It might have something to do with your computer or something. My v6 got 12-14mpg and we couldn't ever connect to the computer. Just a guess.

Shackleford

iTrader: (12)

How's your cat doing? Is it running rich?

Donohue96M6Z28

iTrader: (64)

I dont have any cats...

GulfM3

iTrader: (14)

A fuel injector that is stuck open and leaking fuel into a cylinder after you shut the car off would kill your mpg and might cause your car to seem like it has less fuel every time you shut it off and restart. Thing is, I don't think injectors sticking open is a very common failure. Use a mechanics stethascope to listen to your injectors, you should be able to hear them all click and they should sound similar, listen for one that is really loud, grinding or making no sound at all.

How are you calculating your mileage, pencil and paper every time you fill up? T/A's don't have a MGP display do they? If you are seriously getting 7 mpg I would guess you are leaking fuel from somewhere, because if you're actually burning all that fuel its going to be really rich and run like ****. Have you pulled the plugs? if so what did it look like? Was just ONE plug black indicating a leaking injector? If your plug looks normal, not black and sooty I would be 99% sure you have a leak somewhere.

Is your nitrous hooked up to the shrader valve on the fuel line? check that area for a crack in the rail, there was a guy a while back that had a bunch of lines and switches hanging off the shrader valve and it cracked the rail... was that you? If you park your car in a garage does it smell like gas after you let the car sit for an hour or so?

Keep us posted with what you find out.

ws6killer

iTrader: (4)

In my 2000 5.3 l pickup i experienced these same problems and the fuel pressure regulator was the culpret. you can pop it off and blow into it and see if it blows straight through. I fit does it is bad. Also if not a leaking injector you could have a ton of carbon build up. run a can of sea foam through the tank and see if it does any better. My hci car averages around 13 in stop and go traffic. 23-24 highway

Donohue96M6Z28

iTrader: (64)

Lol, ya man that was me. I replaced the leaky fuel rail, but still am getting shitting gas mileage. I didn't hook up anything to the schrader valve on this rail. I'm calculating my mpg by filling up the tank, driving, then filling it back up. And dividing the total miles, by how many gallons I had to put in the car to fill it back up. When the plugs were changed, all plugs were black and sooty, but the drivers side seemed to have more... Also I haven't parked my car in the garage in a while...

Donohue96M6Z28

iTrader: (64)

Aah. A few of you know this story... But Lethal changed my fuel pump/fuel filter a few months ago. After the swap, I noticed my car was taking 3-4seconds to start... They said it was probably a bad fuel pressure regulator. They had a "good, used one" laying around the shop, so they installed it... maybe it wasn't good

And I've ran a bottle of Lucas... should I do seafoam as well?

Pitbull329

iTrader: (3)

Try seafoam out. Sucks that you're still having issues with that bullshit man.

My fuel needle does the same, after I turn on the car, the needle goes down as if I used 2 gallons (about 1/2 of a 1/4). But after driving around it usually goes back to its "regular" spot.

SHovV

iTrader: (1)

my car does the same thing. but mine needs to be tuned again, it runs hella rich and has a 2.73 gear in the rear end of a M6 car so that doesnt help lol hope you figure yours out man

SLV_WS6

iTrader: (48)

Its the mice maybe they moved from the glovebox to your gas tank.....

1bdBULLITT

iTrader: (17)

I have done my own and had the fuel connectors that hook up to the fuel pump on the outside of the tank leak once, I would check into that as well. I cut the trap door so its easy to check mine but don't know how lethal did your install.

Super-Bat

iTrader: (38)

At least ya'lls needles work. I fill my car up and me needle drops to empty. Only time I ever see "full" is when I turn the car on and the first 10 minutes of driving, then it drops to empty. Lol.
Good luck man, 7mpg sounds terrible.

SiL3NtXWS6

iTrader: (17)

sell it.

Mr. Hyde

iTrader: (10)

That car seems to be more than you are capable of handling on your own.

WeeWolf

iTrader: (16)

Is the computer programmed for the correct gears? Wasn't that car an auto, maybe your mileage isn't reading due to the wrong gear sized programmed in the pcm.

Donohue96M6Z28

iTrader: (64)

Ya man, it used to be an auto. But it was swapped to a 6spd before the tune. Also, I never had this issue up until a few months ago.

I forgot to mention... I notice a slight hesitation/sputter if I "hold" the RPMs at ~2500+ RPMs

SSilverSSurfer

iTrader: (8)

no **** man, seems like theres something new everyday

Donohue96M6Z28

iTrader: (64)

I want to keep it, and I'm willing to pay. Just don't want to go to a "regular" shop to get it checked out.

Firechicken1995

iTrader: (1)

i think you just need to get that car on a dyno with a good tuner and log it and see what everything is doing, if everything in the log looks good then you need to start looking at individual components for faults. do you have a wideband gauge by chance? wonder what the A/F ratio is. do you dive it around time in like 2nd all the time keeping the rpm up? i know when i have my 95 T/A i had 4.10s and would cruise in 6th gear at like 30mph netting like 18mpg in the city.