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Terrible Gas Mileage

G

goose

New member
I drive a 1990 GP LE with the stock 3.1 V6. It has about 67,000 miles on it, 2/3 of which have been in the four years i've owned it. Recently I've only been getting about 7-10 MPG, which is ridiculous, and I can't afford. Anyway, I have a few thoughts about possible causes, and was wondering if anyone has had a similar experience, or has any ideas, I need to get this fixed ASAP.
 


Start wit the typical maintnance things and go from there:
Fuel filter
Air Filter
Spark plugs
Spark Plug wires
coil packs
clogged cat
fuel pump
 
Well, the problem is that I have no real facilities to do a thorough inspection (the college parking lot isn't the best choice), but what i've looked at so far says:

the air filter is clean and un-obstructed

the fuel filter, to the naked eye, appears to be in good condition (Can't get far enough under the car to get it off)

spark plugs are a real pain in the a$$ to get at, You would have to remove the coolant res and possibly the dog bones to get at them well, I pulled the coolant res and disconnected the wires: connections all appear to be clean and not corroded.

Nothing appears to be leaking from the tank, or fuel anywhere (just about everything else on that car does leak)

the exhaust has been replaced from the cat back, but it is the original cat and it appears to have some pretty significant rust damage.

Thats about all I can check into with basic tools and no lift.
 
How does it feel when you really step on it? Also, does it idle like it should or does it feel rough?
 
running just as good as it was before this started? and you cant just look at a converter and see if its plugged, same with the fuel filer...lol
 


What you need is to put it diagnotic softeware so you can monitor all functions of the engine. For example, if the engine coolant temperature sensor was reading incorrectly, you could easily see what data the sensor is giving the computer, and will greatly help diagnos the problem.
 
It has about the same level of acceleration.

The idle is a little on the rough side.

And yes, I know that you cant tell if a cat converter or a fuel filter is the problem just by looking at them, I was more indicating their age/if they had been replaced (neither has)/ if they had any major external damage.

I can tell both are original because the first owner of the car had the whole thing undercoated, so the various things which have been replaced do not have the undercoating.
 
WINALDL is an odb1 program that I use on my Monte SS and my 88 Chevy pickup truck, it is freeware, and a cable must be purchased or constructed to connect to the vehicals ALDL plug. It you have a laptop computer you can drive along down the road and watch in real time all sensors and functions, and data log. If your serious about working on your computer car, it is a vital tool to diagnosing problems.
 
Buy a locking gas cap, one member on here said he got one for his car and his fuel mileage increased significantly.

Oops didnt notice how old this thread was sorry.
 
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I have a 96 3.1, and my poor gas millage is from the o2 sencer. the one that is on the manafold. after that im doing a tune up and a fuel filter. i hope that helps you out.
 
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