Is it? This is when i'm not heavy on the gas, when I am it goes down to 10-12mpg.

 

yep, 17 is a little low even when you're leadfooting it everywhere...normal is in the mid 20's generally.

 

Right now i'm getting about 23 mi but I have a bad exhaust leak. Can that effect my mileage?

 

I have the same problem, and I have gotten 2 different answers: no, and yes. The person who said yes said that the leak (which on mine was right on the manifold) said that it lowered the compression. I highly doubt it, but it was from a trusted source. Perhaps someone else could shed some light? But as for me, I don't really think a leak would make much difference...

 

How the heck is an exhaust leak going to effect the
compression of the motor????

The ONLY thing that exhaust manifolds do is route out
the spent exhaust gases from the combustion chambers.

The only thing that an exhaust leak will do is cause
an annoying sound, to some degree. Also may cause
the check engine light to come on depending where and
how severe the leak is, I.E. right next to the 02 sensor,
causing the 02 sensor to have erractic or faulty readings
due to the improper flow of the exhaust gases passing
by the sensor.

The only things that I know that effect compression
are internal parts of the motor. Like worn compression
rings, sticking valves, bent valves, head gasket deformed
or leaking, warped head, etc.

An exhaust leak can cause a performance problem,
but is rare on occasion and usually has to be a very
severe leak, like a cracked open converter, rotted out
exhaust , an exhaust leak at the EGR valve, stuff like that.

 

well if that leak is by the O2 sensor it can very well cause poor fuel economy, well the way the o2 operates any change in flow will change the parameters. A leak before the sensor could cause a lean condition, a lean condition in a CC car= ECM more fuel poor fuel economy. Sooooo many double standards with computers small things can drive you nuts.

 

Mine gets around 17 in town, and around 23-25 highway.

 

i get about the same. 17 city/20ish hw

 

I get about 17-20 mpg city, depending on the mood my right foot is in, and about 27-29 mpg highway, and that's at 6500 ft. altitude. Down closer to sea level, I got about 20-25mpg city, and as much as 33-35 highway. Sounds like you need a tuneup. As far as exhaust leaks are concerned, an exhaust leak may affect the amount of scavenging that occurs, but it wouldn't affect your compression, since the exhaust valve is closed during the compression stroke.

 

I just tanked up today and I got 24.1 MPG. Almost all of my driving is on the highway. Heh, now that I got my horrible exhaust leak fixed I hope to get some slight better mileage. I wont have to lead foot it up hills anymore since the power is back.

 

I get 21-24 mpg in the city and 26-32 mpg on the hiway. When you live in a hilly region, you can coast for quite a while without having to touch the gas.

 

I don't know what my V6 3.1L Camaro gets right now, because
it's off the road for the winter.

But I think I remember getting about what most of you guys
have been posting, like around 17-19MPG in the city, and
18-22MPG or so on the highway.

A worn out/bad 02 sensor can definitely cause poor fuel
economy. You can't really tell on our "OBD 1" equipped
vehicles, because the "old style" emissions control is not
as strict as the newer "OBD 2" systems today. If your
02 sensor is original, or your in question about it, I would
replace it. It's fairly cheap, and not that hard to do.

You can get a factory equivilent "Bosch" 02 sensor at like
Autozone. Sometimes those 02 sensors can "freeze" up
inside the treads of the exhaust, so be warned!!!

 

Thing decided to get worse, now its getting 12ish. It will vary every time I fill it up, sometimes as low as 12, or as much as 20. All under the same driving conditions. Getting rid of the thing neway I think.

 

12mpg thats awful, hows your motor running?

 

Do you spend an excessive amount ideling? That might explian some of the low gas mileage.

 

No, not really much idleing. It runs really sometimes after it drives about 10 miles or so. Other thing is, it idles warm around 1100, cold between 1500 and 2000.

 

There's a lot of problems that can can cause poor gas mileage:

1) Timing:
advanced timing can give you more fuel delivery and
cause poor fuel economy. Make sure that your timing
is in spec. Also if you run one of those "chips" in your
car, make sure it's timed right for it. Those performance
chips "alter" the factory's air/fuel ratio and may cause
poor gas mileage as well. But they actually suppose to
give you optimum fuel mileage, but can vary from vehicle
to vehicle, and also from different computer chips too!

2) Low tire pressure:
Low tire pressure can DEFINITELY cause poor gas mileage!
I noticed this after the first time I stored my Camaro in the
winter. After taking it out of storage for 5 months, I forgot
to check my tire pressures and just drove like that for
three days! My fuel gauge went down quick! I then checked
my tire pressures, I noticed they were down to 15 psi all
around! I then pumped them up to around 30psi. After
that, no more poor gas mileage.

3) Tune up:
If your spark plugs are gas fowled, change them! Even if
your car runs ok, it can still have fowled plugs. Also remember
to check your distributer cap, rotor, and wires for wear too!
If your plugs are excessively fowled, you may have leaking
fuel injectors. Fuel injectors tend to "leak down" into the
combustion chambers after the vehicle is shut off for a while.
But even then, that's still not good. The fuel injectors may be
worn out, and need replacing if they leak down too much.

4) Air flow:
If you have a clogged up or dirty air filter, change it!
This will cause bad breathing for the motor and "choke"
it, which will then cause bad gas mileage too! Also check
your throttle body for carbon/sludge build up too! Again,
you choke the motor's air when there is insufficient air flow!
Your car can still run ok with these problems. But of course,
to some degree. If excessively dirty, will cause drivability
problems such as bad gas mileage. Check your PCV valve
too, it doesn't hurt to change it if it's in question!

5) Emissions:
Even if you have no check engine light on, a bad 02 sensor
can cause poor gas mileage. I changed mine like 2 years
ago, because it was original with like 68,000 miles on it.
They are fairly cheap, like around $20 at your local Autozone
or auto parts store. I would recommend factory replacement
one, but may cost more.

I'm I'm missing somthing here, but this is what I came up
with for now. I hope you read this and it will help you out!

Later.

 

Thanks for the ideas.
Timeing-Maybie, but I need to get a timeing light or somthing to check that don't I?
My spark plugs and wires were done about 4,000 miles ago, so those should still be good.
Air filter done 4k ago also.
Could be the o2 sensor

Forgot to mention, when its running bad, or sometimes if you rev it, it reaks of gas.

 

I have owned a 91 since new and new and now with 140,000 miles on it it always gets 23-25 no matter how I drive it.

I would change the O2 sensor, and probably the coolant temp sensor. this is of course assuming timing is correct and spark is hot!

does it smell gassy when you start cold? when you pull up and shut it off?

good luck

Don

 

Have you scanned it yet? This would tell you a lot. Right off your idle is too high. Should be 650 - 700 RPM. Is there a working thermostat in the engine? Reeks of gas when you hit it, hmm, maybe injectors are bad. Could also have a bad fuel pressure regulator. Pin hole in the diaphram does two things: pressure goes too high, fuel is pulled diectly into plenum though regulator vacuum line.

Can either throw parts at it and hope, or start checking things. Pull the vacuum line from the reg and check for fuel, if so then bad regulator. Have any exhaust leaks? Broken exhaust manifold bolts? This will allow air into the exhaust with the O2 sensor reporting back to the ECM that it is lean, ECM responds and adds fuel. Too much fuel.

Hook up fuel pressure gauge. Pressure OK? How fast does it drop when the engine is shut off? Fast, then maybe the injectors are leaking.

Should be getting 26.5 highway and 20-22 city.

RBob.

 

[QUOTE]Originally posted by RBob
[B]Have you scanned it yet? This would tell you a lot. Right off your idle is too high. Should be 650 - 700 RPM. Is there a working thermostat in the engine? Reeks of gas when you hit it, hmm, maybe injectors are bad. Could also have a bad fuel pressure regulator. Pin hole in the diaphram does two things: pressure goes too high, fuel is pulled diectly into plenum though regulator vacuum line.

Can either throw parts at it and hope, or start checking things. Pull the vacuum line from the reg and check for fuel, if so then bad regulator. Have any exhaust leaks? Broken exhaust manifold bolts? This will allow air into the exhaust with the O2 sensor reporting back to the ECM that it is lean, ECM responds and adds fuel. Too much fuel.

Hook up fuel pressure gauge. Pressure OK? How fast does it drop when the engine is shut off? Fast, then maybe the injectors are leaking.


See, I knew I forgot some things! All this stuff above should
be checked out, especially now you told is that you have a
fuel smell! First off check the whole car over for any signs
of fuel leaks. The fuel lines, fuel tank, filter,etc. The pressure
regulator and injectors are harder to check , cause they are
under the intake plenum. But with good lighting and a good
eye, you can still check around the injectors and regulator.
Also, do a fuel pressure leak down test. You need a fuel
pressure gauge. One with a GM adapter that goes to the
shrader valve behind the motor. Once the fuel pressure
gauge is set up, turn the key to run, don't start the car
yet!


Check the gauge. It should go up to around 30-40 psi.
I don't know the exact spec. for the pressure off hand.
Still, if it does but then starts to leak down, you may have
a bad regulator or fuel pump or even injectors!

To check for a bad fuel pump, leave the gauge on , start
up the vehicle. While it's running, raise up the throttle
and let it back down. Look at the gauge while doing this.
The gauge should go up , then back down to normal
spec. when you let off the throttle. This means the pump
is good! Usually the gauge should go up to about 10psi
above spec. when raising up the throttle.

Also, for the high idle, that will cause bad gas mileage
right there. You need to check why the idle is too high.
A lot of things can cause idle problems. IAC valve is
one of them. Another is timing. Yeah, you need to get
a timing light for that.

If you can't do any of these checks, I would suggest
taking the vehicle to a trusted mechanic or a trusted
dealer. But prepare to pay a diag. fee right off the bat!
Every place charges a diag. fee to check the car over
first. Usually it's like an hour or so labor. Anywhere from
$60 to as much as $100!!!

I can go on and on to help you, but it will turn into a
novel here!

Hope you find the problem!

Later.

 

Could this be the fuel filter doing this by any chance? That or the pump wouldn't cause bad milage though, correct?

 

Yep i use to have that problem all i can say is timing is everything, you may think you have it right by ear but nope. Be sure to pull the brown wire black connector.

I now get 22 city 32 highway (no A/C on)

Also thought had had a tranny problem because of a hard shift into 2nd, nope it was just losing power between shifts.

Tune up and timing does the trick!! Smooth shifts all the time now.

 

A partially clogged fuel filter can give you bad gas mileage.
A bad or weak fuel pump will more than likely give you
a drivability problem, like a hard start or stalling, lack
of power, stuff like that. I would change the fuel filter
if it never has been changed. Even if it has, but not
recently, I would still change it. You can get one cheap
at your local auto parts store for like $10.

I would check on that fuel smell first! That can be
dangerous! Have someone check the car over on a
lift for fuel leaks. Remember to check the injectors
and fuel rail and pressure regulator too!

You have to run a through check on the car before
guessing what the cause is. I would recommend
having someone do a complete analysis on the
vehicle. Have the car checked for fuel leaks, the
fuel pressure tested, the timing checked, etc. Just about
anything on the vehicle can cause bad gas mileage.
But a fuel smell is, of course, related only to the
fuel system. But, the evaporative emissions system
can give you a fuel smell too! A leaking charcoal canister
can definitely cause this! It could have a crack in it, or
just a little hole in it. Also, if it weights very heavy, it
most likely got "liquid fuel damaged" cause only fuel
vapors are supposed to go through those!

Hope this helps.
Later.

 

HELL NO MAN
it's not bad



but then again i just ran like 8mpg last week

so don't feel to bad

 

I got just under 13 mpg last tank. Maybe it's because everything on this car seems to be original except the intake and cat-back which I replaced. Cat is definitly bad though it seems the honeycomb stuff has flown out already, and the wires are original and I'm almost sure the plugs are the same. Engine runs fairly strong and smooth but it idles a bit high, 900 when warm, but it also starts on cold mornings better than my dad's new 4runner and it stays in the garage.
David

 

I actually have the fuel filter. How do you put the thing in? Which nut actually turns, the one on the filter or the one on the line. I tried to get it off, but i'm afraid to turn it to hard, because i'm not sure which to turn and I don't feel like bending the fuel lines.

Its a 91 RS, with the fuel filter by the drivers rear wheel.

 

how do u guys figure out your MPG? do you account for idling time in the mornings and just sitting in traffic?

 

All Camaros with Fuel injection have the same style fuel
filter in the same area ( but not sure for TBI). Anyways,
the nuts on the fuel lines turn. Not on the filter. But BE
CAREFUL! I would use penitrating oil on those nuts first
and let them soak for a while ( also called WD40). You
will have a better grip on those lines with a flange style
open end wrench. If you are hesitate about doing this
yourself, and not want to screw up the lines, I would
have someone replace it for you. It should only cost
about a half hour labor. If more than $35 for the job,
your getting ripped off!

P.S. you will need TWO wrenches for this job, one to
hold the filter nut end, and the other to break free and
turn the nut on the line. I'm not sure the size, as I haven't
done one since last Sept.

Hope this helps.

 

The easiest and most accurate way to estimate MPG is
to let your gas tank run as close to empty without getting
stuck somewhere from letting it run on empty too long.
Best way, let it get to 1/4 or maybe 1/8 of a tank left,
full up the tank.

Then, set your tripometer to zeros. Drive again until
1/4 tank left, refill tank. Now , take down the miles
set on the tripometer. Finally , divide the mileage from
the tripometer with the amount of gallons it took to
fill the tank, you now have your MPG.

Long idling and stop and go traffic will effect your MPG.
This effects it more than any other type of driving. You
can't estimate MPG on driving conditions, you can only
do the above steps. There is no other way, as far as I
know.

Hope this helps you. Any questions, reply here.
Will be happy to help you.

 

Another thing I noticed, is the AC compressor in my car turns itself on and off when it is idling, i'm not sure if it does this while driving as well.

 

Since you are from New York, I assume that it is just as cold
as it is over here in New England.

So, If you have your defroster on, it turns on the A/C compressor
so the defroster can work. A/C compressor shutting on and
off is normal. That means that the "pressure" of the freon
is good. The A/C compressor cycles on and off, this is how it's designed to operate. So, again, this is normal, every vehicle with a properly working A/C system will do this.

 

Doesnt the A/C clutch engaging and disengaging reduce MPG?

 

It does this withough any heat or cooling turned on, but ok, Ill try the filter see if that does anything, then move on from their.

 

To some point, yes.

Because once the A/C or defroster is turned on, it adds
a load to the engine. Thus, having a parasidic drag on the
motor, will make the MPG lower. Even though there is
always a parasidic drag on the motor just from the
compressor being there to begin with, it makes it even
more when the A/C clutch cycles on and off.

Power steering and Secondary air pump also adds
drag to the motor as well. Any accesory drive can
lower MPG.

 

The A/C compressor should not be cycling at all then!
Only if you have the A/C or defroster on should it be
cycling. You may have a problem with your A/C system
then. A constant cycling of the A/C will definitely cause
your lowered MPGs. But not that much like you stated,
I don't think it should anyways...

 

Wait a minute, you are from New York, right? You are
driving around in New York? The constant cold weather
will lower your MPG, don't forget that! Especially if you
warm up your car for like 10-20 minutes every morning.
This weather severely reduces MPG. I went from 25 MPG
in the summer, to 17 MPG right now, with below freezing
to below zero temps! This is all highway driving too. So,
if I were to drive more in stop and go traffic, I wouldn't
be surprised to see it drop to 14 MPG.

 

I let my car run for 2-3 minutes before I drive it, I do this about 2 times a day so it shouldn't be affecting anything too much. The cold weather thing is probably it, althought it doesn't make much sense to me. The AC is not constantly cycling, it just likes to turn itself on for a few seconts, back off, then on again after a few seconts, it only does it when it feels like it thought, its not a constant thing.

 

Ok, your car takes a lot longer to warm up in the winter
than it does in the summer.

The temp. gauge takes longer to move up to the normal
or "middle" area than in the summer.

All this is related to the OUTSIDE temp.! Your vehicle
DEPENDS on the outside temp. reading to calculate the
engine's proper air/fuel delivery. So, the colder it is,
the colder the air is , correct? This makes the air a lot
denser than warm air.

Fuel also takes longer to burn in colder temps. That's
what kills your MPGs!

All of this true. And now I'm 90% sure that's why your
car gets poor gas mileage. My car does, and just about
everybody else who drives in the winter time around here
and around your area.

 

I don't know how you can stand only 2-3 minutes of the
car being warmed up. Unless it's a little warmer over there
in the morning, cause I need to warm my car up at least
10-15 minutes to have nice warm air in the car.

 

My car usually doesn't heat up past 120 degrees or so, unless it idles for a while. So I don't get much heat even after the thing has warmed up. Untill I do the thermostat anyway. This car is just a whole mess of problems, nothing works right.

 

It could be a thermostat sticking. Like not staying closed
enough to keep the engine to operating temp. or taking
too long to operating temp.

Honestly, I never drive my Camaro in the winter. It's
dangerous for me anyways. They suck on snow. They
are only made for spring/ summer/ fall weather with
barely any rain conditions. I used to drive my Camaro
in the winter years ago, but was too dangerous and
I got frustrated with it, so I bought a winter car.

The MPGs that I stated are from my '95 Taurus 3.0L
with only 30,000 miles on it! A totally different car
with the same POOR gas mileage, and I don't have
a single problem with my car.


Sounds like you need a new or newer car! Anyways,
hope things go well.

Later.

 

Gased up today I went 261.65 miles and tanked up with 9.8 gallons. The needle was staying in the middle of the warning line just before E mark. 26.698 MPG :rockon: heck yeah my gas milleage has been going up and up the last few weeks after I fixed that driver exhaust leak. 3 weeks ago I was getting 24.1 mpg ALL HIGHWAY DRIVING. LOL the funny thing is now my pass side has a slight exhaust leak LAMO one side to the other.