bad gas milage?

[messiveian]

I let my car run out of gas then put in $10 dollars of gas which came out to 3.333 gallons. I then drove until i was completly out where i ran out of gas. (i had a gas can in my car while doing this of course) i did this a number of times and would get anywhere from 22.5 mpg to 24.9 mpg. This was 75% freeway at about 65 mph. i would think for a 4 cylinder i would be getting better gas milage. I get a CEL light once in a while but if i shut the car off and turn it back on the code goes away.
my car has 145,500 miles on it right now
I have had the car since november 2006 and i have only done oil and air filter. I am thinking about replacing the spark plugs, fuel filter, and possibly the o2 sensors and the PCV valve because its cheap. I also noticed i had about a 3 inch cut in the Hose that goes from the PCV down the the intake?? ( its not the one from the crank case to the PCV and its not the one from the PCV to the air filter)

Thanks

[Nighthawk243]

The 1995 doesn't do well on gas milage. I averaged 22mpg.

[350F]

It would be a lot easier to get a true gas mileage reading by filling your tank up, resetting your trip, then running it close to empty and filling up again. Divide the # of miles on the trip by the # of gallons of gas it took to fill up your tank again.

It also depends on your driving habits, routes everyday, and condition of the car.

My car is rated at 22 city, 29hwy, and I do probably 70% city driving, and I average 29+mpg.

You can start by making sure your tires have the correct tire pressure. (I run mine at max side wall PSI). Also, when you are on the highway, what speed do you go? I set cruise on 60mpg and hang in the right lane. You'll gain probably close to 15% better mileage just by slowing down from 70+mph. Also, try to keep the RPMs down when accelerating. Unless totally necessary, I never go over 2000rpms.

[HornetGT141]

I just used St.Louis Gas Price's Fuel Logbook (http://www.stlouisgasprices.com/):P to calculate my crappy 16.85 MPG. :(

[Big Dawg 23]

You might want to check over you car. I have a 97 and get 23-25 city beating on it and 29-31 freeway. The mileage of course climbs higher when I lock the cruise at around 65(2K RPM's). The more I do over 70 the mileage starts to drop. MY 03 GT gets about 20-22 city and 27-29 Freeway.

[HornetGT141]

Yeah I have figure it has to be the Front O2 which was just tested out to be ok resistance wise (maybe I should just get it changed anyways) or the EGR Valve deciding to stick open. One is covered under warranty and the other isn't. :P

[messiveian]

yea i figure im going to get my fuel filter changed, spark plugs, PCV valve, and im going to get my ripped PCV hose hose replaced because that probably isnt helping to much then hopefully i will be good to go

[rixGAphx]

Originally posted by messiveian
PCV valve, I thought the 4-cyls didn't have an actual PCV valve??
and im going to get my ripped PCV hose hose replaced... Wasn't that the thing in the photo with the zip-ties?
Didn't you fix the actual rip already??
At least duct-tape it, if not simply buy the hose for a couple bucks.

Yeah, a raw vac leak into the intake manifold is gonna make for lousy gas milage.
Regardless of how little gas your foot wants to use, the 'puter will always addenough fuel to compensate for the oxygen in the exhaust.
So if there's a giant vac leak, the 'puter *almost* thinks you're flooring the gas pedal.

[Matt95GT]

First of all, the cracked hose needs to go. If that one cracks, you have a massive vacuum leak... if it rips more, it may not even idle at all. You SES light/code is most likely caused by this. When the SES light is on, I've noticed the "safe mode" on mine tends to run the engine very rich... not good for gas mileage.

You don't have a PCV valve. That box is an oil/air separator that usually does not require any service.

Do all that first, then ignition system inspection/plug replacement (AC Delco platinum) next.


Originally posted by 350F
It would be a lot easier to get a true gas mileage reading by filling your tank up, resetting your trip, then running it close to empty and filling up again. Divide the # of miles on the trip by the # of gallons of gas it took to fill up your tank again.

...
Also, try to keep the RPMs down when accelerating. Unless totally necessary, I never go over 2000rpms.

Yea, don't try to calculate fuel economy on a part tank, and you'll need to take averages to get reliable data.

I agree that driving habits make a big difference, however, keeping RPM down on a Quad 4 is counterproductive. The Quad 4 is not efficient at make torque at those low RPM's, and will actually consume more fuel.

Originally posted by Nighthawk243
The 1995 doesn't do well on gas milage. I averaged 22mpg.

Odd... my 95 2.3 averaged 28-32 when mostly stock. Even with 152K miles, supercharger and modded fuel system/tune (runs extra rich at higher throttle) I still get 27-28 MPG.

[hoytprostaff]

If messiveian had a pcv valve and the hose leading from it to the manifoldwas cracked open, would this seemingly small hole cause noticeable idle issues of a bad vacuum leak or just the bad fuel mileage?

[rixGAphx]

Any hole into the intake manifold is a 'vacuum leak'.
A small leak (like a 1/8" tube coming loose from a nipple) will cause extreme rough idle.
The effects of a large leak, such as the 'ripped' tube that he described, are harder to determine.

Excessive fuel consumption is NOT a usual symptom of a vac leak, small or large.
Frankly, we don't know if his milage is truly bad (becasue his test method' is a bit unorthodox), nor what the cause might be.
This ripped hose is a known defect inhis intake, so it *might* be to blame.

At idle, an FI engine has the throttle SHUT, and the small amount of air necessary for combustion is being controlled thru the Idle Air Control valve, by the IAC motor.
At idle, the fuel injection is determined by the computer based on default mapping.
When the throttle starts to opened, the computer senses it thru the Throttle Position Sensor; and determines the fuel injection based on exhaust readings of the O2 sensor.
A small vac leak has a large effect at idle, and virtually no effect on higher rpm running (because the O2 sensor adjusts the richness accordingly).

He calls it a 'rip' in the rubber tube; it may be quite large, but it's acting like a flapping door.
The amount of air that leaks thru it may vary, and we really can't predict how the computer is gonna respond.

I doubt this clarifies much, but I don't think we can get any closer to an answer without actual dyno testing in a laboratory.

Hope this helps,
-Rick

[hoytprostaff]

I had to ask because i cracked open this same tube when i was replacing my fpr and I couldnt notice any effect on the idle. I changed it anyway but I did wonder if this should have had a bigger effect. Its sort of like when I would take the vac line of my fpr; there was almost no change. I hope thats not a bad thing and it didnt seemed clogged.

[rixGAphx]

Originally posted by hoytprostaff
I had to ask because i cracked open this same tube when i was replacing my fpr and I couldnt notice any effect on the idle.
I changed it anyway but I did wonder if this should have had a bigger effect.
Its sort of like when I would take the vac line of my fpr; there was almost no change.
I hope that's not a bad thing and it didn't seemed clogged. It's not the same tube.

You have a V6, and all the V-6's have conventional PCV valves, with a 1/4" tube that connects them to the intake manifold.
If your car was just setting there idling in the driveway, there should have been some effect.
If you had driven, and allowed the engine to rev then drop to idle, there would have been much more effect.

He has a 4-cyl, therefore he has no PCV valve; so whatever his tube is/was, it must be different from whatever tube you cracked.
His tube was about 1" diameter, IIRC his pic of last week.
* * *

I dunno why you wouldn't have noticed anything when your PCV hose cracked.
But you didn't, so there: Evidence that a minor vac leak might have no or little noticeable effect on teh V6 at idle.

[hoytprostaff]

I think the way mine cracked left such a barely open hole that it wouldnt have made much of a difference. Anyway, thanks for the info....I promise to stop hijacking this thread.

[messiveian]

ok i was wondering about the pcv valve because i couldnt find it anywhere. Also i have noticed when my SES light is on i get horrible gas miliage.

Also rick the pic i posted last week or whenever was the tubing going from the crank case to the small black box. I have since gotten that replaced and it was a 9/16" hose and i replaced with with a 5/8" hose for 75 cents and fits perfectly. The hose that is ripped now is the one from the black box down to the intake. Also the rip in it is about 3 inches long and starts right at the black box. It looks like a knife sliced it.

i just took a long trip and i filled up my tank completly before the trip and then when i was near empty i filled it up completly and it took in 14.68 gallons.

i went 354.7 miles all on the highway with cruise on at 67mph so im only getting 24.162 mpg so thats probably pretty accurate. but i would still think i would get more.

my SES light came on for about 50 miles before i stopped at a rest station for food but when i started up the car the light didnt come back.

[rixGAphx]

Originally posted by messiveian
I have since gotten that replaced and it was a 9/16" hose and i replaced with with a 5/8" hose for 75 cents and fits perfectly.Cool.
The hose that is ripped now is the one from the black box down to the intake. Also the rip in it is about 3 inches long and starts right at the black box. It looks like a knife sliced it.I don't know what the 'black box' is (air filter box???) nor what you're calling the 'Intake', since there are about 4 or 5 things on any engine thru which air passes that could be called an 'Intake somethingorother '
A pic would certainly help.
However, any tube that's ripped/sliced 3" long either STOPS the engine from running, or isn't part of the actual 'induction' system (basically, the airflow stuff downstream from the throttle body/carburetor inlet).

i just took a long trip ...with cruise on at 67mph so im only getting 24.162 mpg.Nope, that's about right, especially with the below-noted 50 miles that you drove at about 15 mpg.
... my SES light came on for about 50 miles...It' ll do, that, especially on a 12-yr old car that's not yet in perfect tune.
Whenever the CEL comes 'on', the computer has reverted to an ultra-rich fail-safe mode called 'open-loop.' with absolutely sh!tty gas milage.

Put some duct tape on that 3" gash, to keep dirt and crap out of whatever part of the 'intake' that is.

Good luck,
-Rick

[messiveian]

ok thanks and the hose im talking about goes from not the air filter but a black box that connects 3 hoses right in front of the engine. The 3 hoses are ( the hose from the crank case to the black box, the hose that goes from the black box to the air filter, and then another hose that goes from the black box down to the intake that is infront of the starter). its the hose that goes from the black box to the intake infront of the starter. i guess the black box acts as a PCV valve and filters out the air returning from the crank case.

but anyway im going to get that replaced.

i guess i need a hybrid lol

[HornetGT141]

I believe he is talking about the MAP sensor housing.

[Matt95GT]

Originally posted by messiveian
ok thanks and the hose im talking about goes from not the air filter but a black box that connects 3 hoses right in front of the engine. The 3 hoses are ( the hose from the crank case to the black box, the hose that goes from the black box to the air filter, and then another hose that goes from the black box down to the intake that is infront of the starter). its the hose that goes from the black box to the intake infront of the starter. i guess the black box acts as a PCV valve and filters out the air returning from the crank case.

but anyway im going to get that replaced.

i guess i need a hybrid lol

Actually there's 4 hoses to the oil separator:
1. Timing housing to separator
2. Separator drain to pan (converges with oil fill tube)
3. Separator to intake manifold (vacuum source, goes to rear of manifold)
4. Separator to intake plenum (to flex tube after air box)

Sounds like #3 is the cracked hose, which happens to be the one that will give you problems if leaking.

Correct... it is used instead of a PCV system. The box contains a maze of little plastic channels, letting the oil condense and drain back to the pan, and the air (with any remaining vapors) back into the intake.

Originally posted by HornetGT141
I believe he is talking about the MAP sensor housing.

He isn't. The Quad 4 MAP has a tiny piece of thin tubing, and on a speed-density fuel-managed engine, it probably wouldn't even run if it was cracked.

[HornetGT141]

Originally posted by Matt95GT
He isn't. The Quad 4 MAP has a tiny piece of thin tubing, and on a speed-density fuel-managed engine, it probably wouldn't even run if it was cracked.

It doesn't even have the housing itself? That was the black box that I'm talking about. I'm just a nub...forgive me. :P

[Matt95GT]

Originally posted by HornetGT141
It doesn't even have the housing itself? That was the black box that I'm talking about. I'm just a nub...forgive me. :P

Must be a V6 thing.

The oil/air separator is the index card-sized box under the "DOHC" letters. The MAP sensor is mounted just below that separator, in between intake runners 2 & 3...
http://www.fazeshift.org/pics/albums/userpics/08-31-03/DCP03890.JPG

[messiveian]

matt95 is my best friend now he knows everything well him and rick. I still havent got that hose replaced yet because i havent had time but after i go pay my speeding ticket tomorrow im going to get an oil change then pick up a foot or 2 of the same sixed hose and fix it .

hopefully it helps my gas milage and i noticed sometimes after i have driven for a little while and put my car in park the rpms jump up. (dont know what to because there is no rpm guage)