Car question? Update!

[coolVariable]

For some time now my car has been guzzling gas like there is no tomorrow.
Thinking that the air filter was due for renewal, I just went out and bought a new one. But now I#ve seen that the old one is still fine (looks still white with only very little gray residue).
What else could account for the low miles/gallon?




UPDATE:
I took the car to Midas today (it's just down the street) and they hooked it up to the computer ($88 :Q)
They found out it wasn't the O2 sensor (sadly) but:
- the coil pack (the secondary one??) ($189 )
- the ignition module ($402 :Q)

:Q :Q :Q :Q :Q :Q :Q :Q :Q :Q :Q :Q

 

[Nocturnal]

Bad sensor(s) giving you crappy fuel/air ratio. Get those checked out.

 

[bolido2000]

check for dirty fuel filter, dirty injectors, bad O2 sensors

 

[Zenmervolt]

How much has mileage changed? How old is your car? What kind of car is it? How many miles does it have? Need to know all these things.

ZV

 

[ohtwell]

Check the fuel filter.


: ) Amanda

 

[HappyPuppy]

The O2 sensor could cause that problem. Have you ever had a tuneup?

 

[SlowSS]

Originally posted by: Zenmervolt
How much has mileage changed? How old is your car? What kind of car is it? How many miles does it have? Need to know all these things.

ZV

Yeah, it's like someone calls and say "my computer won't start up".

 

[ElFenix]

Originally posted by: SlowSS

Originally posted by: Zenmervolt
How much has mileage changed? How old is your car? What kind of car is it? How many miles does it have? Need to know all these things.

ZV

Yeah, it's like someone calls and say "my computer won't start up".

i love those calls

 

[Zenmervolt]

If you're over 100,000 miles, you probably need to change the O2 sensor. But if it's a newer car, then the Check Engine light should come on if the O2 sensor fails. Of course, some new-ish FI systems don't trigger the light if the O2 sensor goes out. Heck, it could be as simple as under-inflated tires. We really need to know more about the car.

ZV

 

[Eli]

Originally posted by: ohtwell
Check the fuel filter.


: ) Amanda

Hmm.. I would think that a clogged fuel filter would hinder fuel flow, not make it worse.

Does the car otherwise seem okay?

Have the car tuned up, and see if that fixes the problem.. Spark plugs perhaps?

 

[coolVariable]

The car is a 93 Ford Mustang with 73k Miles on it.
My guess it's the O2 Sensor since the Check engine light has been coming on sometimes ...
Good thing i checked with you guys otherwise I would probably have had the oilfilter, spark-plugs, oil, ... changed and it wouldn't have helped.

My mileage went down from ~240 Miles per tank filling to ~160 Miles.

 

[Analog]

cold weather.

 

[malbojah]

Driving short distances on a cold engine also does that. My 94 Saturn sl2 gets about 175 miles to the tank. But driving only 2 miles a day, I need to refill the tank every other week.

 

[BlackOmen]

Originally posted by: yellowfiero
cold weather.

Ditto. Now that we're facing some cold days your car is going to spend much more time warming up. The state that your car warms up in is called "closed loop". In this state your air/fuel mixture is going to be richer and you will get poorer fuel economy while in this state. Now, I believe a friend of mine, who has gone from 26mpg to 16mpg on the highway, is not reaching the open loop state. He likes to crank the heat and is running a colder thermostat. Even in my four cylinder Chevy I havn't been getting the same fuel economy. Early last week I stopped cranked the heat (blower sees a high position of 2 now) and now I appear to be getting better fuel economy then. When I would crank the heater on 4, my engine water temp gauge would start to drop below its normal position. My friend turned the heat down as well and placed some cardboard in front of the radiatior and just got 24mpg on a 350 mile trip.

If you're milage got worse as the temp has really started plunging, then maybe you're not getting out of the closed loop state or you are reentering this state. Turning the heat down allows the motor to retain it's heat, at the expense of your comfort of course

YMMV.

 

[SeaSerpent]

spark plugs and wires

 

[coolVariable]

I don't think the car needs much warming up when it's 85° outside ....

The Check Engine warning and the high gas consumption lead me to believe it's the O2 sensor ...
I don't believe the Check Engine warning would come on for spark plugs.

 

[roncarter]

how about adding some stuff to your fuel??

Not very sure.. but I have the same problem..

 

[coolVariable]

Well, I got 240 per gas filling before and now its WAY BELOW that ...

 

[Zenmervolt]

Originally posted by: coolVariable
The car is a 93 Ford Mustang with 73k Miles on it.
My guess it's the O2 Sensor since the Check engine light has been coming on sometimes ...
Good thing i checked with you guys otherwise I would probably have had the oilfilter, spark-plugs, oil, ... changed and it wouldn't have helped.

My mileage went down from ~240 Miles per tank filling to ~160 Miles.

If the light is coming on and the mileage is way down (typical winter loss even in very cold climates is only 2-3 mpg) then it's almost definitely the O2 sensor. Very early for it to fail, but it fits all the symptoms and it would be triggering the light. You will probably want to change the spark plugs anyway after you fix the O2 sensor though. Right now the engine is running very rich and your plugs will need at least cleaned. Considering that plugs are relatively inexpensive it wouldn't be a bad idea to just change them once the O2 sensor is fixed.

ZV

 

[notfred]

Originally posted by: coolVariable
The car is a 93 Ford Mustang with 73k Miles on it.
My guess it's the O2 Sensor since the Check engine light has been coming on sometimes ...
Good thing i checked with you guys otherwise I would probably have had the oilfilter, spark-plugs, oil, ... changed and it wouldn't have helped.

My mileage went down from ~240 Miles per tank filling to ~160 Miles.

Mustangs have 2 O2 sensors, and they never got fantastic mileage to begin with

 

Check your trouble codes.

Many things can cause poor fuel mileage including but not limited to the following ;

Worn S.plugs/wires/cap/rotor
Plugged or restricted filters/PCV valve
Slipping transmission
Internal engine problems
(Worn timing chain, poor compression)
Dragging brakes
Low tire pressure
Low coolant temperature
ETC.

 

[Evadman]

Originally posted by: Roger
Check your trouble codes.

Many things can cause poor fuel mileage including but not limited to the following ;

Worn S.plugs/wires/cap/rotor
Plugged or restricted filters/PCV valve
Slipping transmission
Internal engine problems
(Worn timing chain, poor compression)
Dragging brakes
Low tire pressure
Low coolant temperature
ETC.

Isn't it time for your afternoon nap And shouldn't you be at work running your shop?

 

[Vic]

Checked the oil lately? I would do that first (and was surprised that no one else seemed to mention it).

 

[Zenmervolt]

Originally posted by: Vic
Checked the oil lately? I would do that first (and was surprised that no one else seemed to mention it).

Oil will not trip the "Check Engine" MIL. Oil will trip the "Low Oil/Low Oil Pressure" MIL.

ZV

 

[Pepsi90919]

Originally posted by: Vic
Checked the oil lately? I would do that first (and was surprised that no one else seemed to mention it).

because it doesn't apply