low mpg.....once again

Mustangless · Dec 14, 2005

Okay, I have had my car for two years and have had bad gas mileage the entire time. The worst I got was 11mpg, the best was 14.5mpg. I usually get low 14mpg, until I installed my street edge converter. After that it went up to 16.9 (i had calculated it wrong and thought it was 19mpg). That was 1/2 hwy/city.

Well, I filled it up yesterday and got 14.2mpg. I was going easy on it the entire time except for two times. Things I have done.....

New TQ converter, this helped performance alot
Plugs, Wires, Cap, Rotor
Air Filter, fuel filter
gutted cats
seafoamed
one new o2
cleaned Maf, this helped performace some

I am happy with the way it performs, but not with the gas mileage. With my mpg, I feel like I should have a 400+hp car, not near stock. I want to figure out what my cars problem is before I start modding. I have read that my problem could be fuel injectors or MAF. I don't want to buy new 19lb injectors (or whatever is stock) and a stock maf then have to change it when I do mod.

Anybody got any ideas of what I should try?

sage2k · Dec 14, 2005

perhaps try looking for a used set

Mustangless · Dec 16, 2005

I have not changed anything yet but have more symptoms. Today while I was sitting in traffic I noticed the rpms were pretty low. Is it supposed to idle at 750? It looks like it was more towards 600-650. Also, it almost went dead a few times, it sounded like it was stumbling. I would not give it any gas, but it acted like I did.

I have not checked my timing but last time I checked it, it was at 12. Could low timing make the rpms lower?

sage2k · Dec 17, 2005

my rpm is roughly 600 idle with AODE according to our stock tach but i hooked up a timing light with rpm gauge on it and i think i was really idling at like 700

HISSIN50 · Dec 17, 2005

Do you know if you are using oxygenated gas right now?

Mustangless · Dec 17, 2005

HISSIN50 said:
Do you know if you are using oxygenated gas right now?

I don't know what that is. I was reading where low rpms could mean a bad maf. It has been cleaned more than once. Wouldn't I get a code if it was bad?

HISSIN50 · Dec 17, 2005

A MAF code - not necessarily.

Oxygenated fuel is used in parts of the country (we have it here). It can lower milage 1-3 MPG in my experience. The gas pumps are supposed to have a sticker letting you know if the fuel is oxygenated and what part of the year this occurs.

Good luck.

mo_dingo · Dec 18, 2005

Replace the other O2 sensor, that would be a first. Next check vacuum and fuel pressure, w/ and w/o vacuum.

Lastly, do a compression test, and see if any are low.
Scott

Mustangless · Dec 18, 2005

mo_dingo said:
Replace the other O2 sensor, that would be a first. Next check vacuum and fuel pressure, w/ and w/o vacuum.

Lastly, do a compression test, and see if any are low.
Scott

I just ordered another o2 sensor. I hope this fixes it.

Mustangless · Jan 5, 2006

Mustangless said:
I just ordered another o2 sensor. I hope this fixes it.

I replaced the o2 sensor and it still is acting up. The car sounds as if it is about to die, then the rpms will shoot up from around 550-600 to 800.

Is there way to check and see if it is the maf causing this, other than replacing it?

urban96 · Jan 5, 2006

check all your vaccume lines...

you only replaced 1 O2 sensor?

Mustangless · Jan 5, 2006

urban96 said:
check all your vaccume lines...

you only replaced 1 O2 sensor?

I got a code for one a year ago and replaced it. I just replaced the other one. I have always heard to check for vacume leaks but how do I go about that? I see all of these hoses and I am supposed to squirt something on them. Is there specific hoses I am supposed to check?

yellowstang1994 · Jan 5, 2006

Whats your tire pressure looking like? I think it's something that is overlooked way too much. Usually I find a friend that has a flat (he didn't realize) or way too much pressure. I make it a habit to check my psi every sunday. I got a few plugs in one of my rear tires and when it goes down a little, i get like 10mpg, lol.

Mustangless · Jan 5, 2006

It has been around 35 but I did install new tires today and they have 33 in them. Before installing them I checked one of the front ones and it was 28. I don't think it has been that low though.

When I installed my new tires Inoticed that my rears were wore in the middle. The drivers side was wore big time on the inside.

95GTV8 · Jan 6, 2006

Hey, i was having the same experience, it was driving me crazy but i finally found the culprit. At 1st i cleaned the IAC with a can of carb/throttle plate cleaner, my car seemed to be happier but once i started it cold in the morning the idle was surging. I checked everything else maf etc so then i began to wonder if i had a small vacuum leak. I found a vacuum leak where the two lines (red/green i think) come off the throttle body and the red line connects to something that feeds into the passenger side fenderwell. Once i plugged this in i had to wait for the next morning for a cold start, but sure enough that was the culprit and now my car idles perfectly. Hope this helps.

ROLLIN5.0 · Jan 6, 2006

Spray starting fluid on all the vaccum lines with the car at idle. When the idle goes up, you found the leak.
Brandon

blk9450 · Jan 6, 2006

ROLLIN5.0 said:
Spray starting fluid on all the vaccum lines with the car at idle. When the idle goes up, you found the leak.
Brandon

lol thats a good way to start a fire, especially with possibly bad plug wires. wd-40 workd and is less dangerous..

ROLLIN5.0 · Jan 6, 2006

blk9450 said:
lol thats a good way to start a fire, especially with possibly bad plug wires. wd-40 workd and is less dangerous..

I've done it dozens of times without a fire, and have heard many mechanics recommend the same procedure. I don't know about you, but I would rather my motor burn a little bit of starter fluid (something designed to be burnt by a motor) than WD-40.
Brandon

blk9450 · Jan 6, 2006

ROLLIN5.0 said:
I've done it dozens of times without a fire, and have heard many mechanics recommend the same procedure. I don't know about you, but I would rather my motor burn a little bit of starter fluid (something designed to be burnt by a motor) than WD-40.
Brandon

so you would rather have your motor burned than oiled with wd-40.... ok.....

starting fluid is meant for startup when nothing else works. spray it on your hand, it totally dries up in a few seconds, making your hand drier than before as it evaporates off, leaving no residue.. spraying that in your motor while running it is not going to be the best thing for your motor. the point is though, starting fluid can catch on fire extremely easy, especailly on a running motor where arcs from bad wires can ignite it.. sure you can do it a million times and not have a problem. thats why they call them accidents

wd-40 lubricates, you know like oil, the stuff in the bottom of your motor, the stuff that gasoline is made from...

HISSIN50 · Jan 6, 2006

Ether is highly volatile. This is not to say that WD-40 is not flammable either (some people use it in lieu of starting fluid).

Another method, though dirty, is to use a little oil can with motor oil - the oil will fill a void and change the idle.

Or use a smoke machine......
Good luck.

low mpg.....once again

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