I'm getting horrible gas milage on my Impala!!! HELP?!!?

[DOODO0]

I just purchased a 01 Chevy Impala 3.8 with 117000 miles on it, and I notice that I'm getting horrible MPG. The miles I put on are half highway and half city, I do not have that heavy of a foot. It is advertised as getting 21 and 30, but I'm no were even near that ballpark, I see that i'm getting no more then 13 mpg combined driving. I checked the tire pressure and its proper and I just changed the oil. The service light is lit up, does that mean i should get a engine tune up? What could be wrong with the car that i'm getting this sh*tty gas milage?? Thanks

[Grant Lamontagne]

I was somewhat worried when I first saw the title of this thread in the Main Index, and all it said was "I'm getting horrible gas."   

Back on topic, a properly tuned engine should run well, but you'll never get the kind of mileage a car is rated at.  You should however at least get into the ballpark.  So, I would consider getting a tune up, as well as look at a whole host of other potential problem areas such as dirty injectors.

I'd suggest taking the car to a mechanic you trust and having him check it out, and maybe hook a scan tool up to it to make sure everything is running properly.  He'll probably have to put a scan tool on it anyway to clear the check engine light.

One thing you may want to check is that the gas cap is all the way on.  I have had a problem with my Sunfire a few times where the gas cap wasn't tightened up properly and that triggered the check engine light.

Def

[NutSAK]

In addition to the regular tune-up items and having the computer scanned, at 117,000 miles, it's probably due for a cleaning out of the carbon from the intake and combustion chambers.  You can have this done at a service station, or you can do it yourself with a can of Seafoam.  I'm not going to go over the Seafoam procedure--buy a can and read the directions if that's the route you decide to take.  The service station will hook it up to a machine to do it.

Pour a bottle of Chevron Techron concentrate fuel system cleaner in the gas tank at a high cleaner/gas ratio (read the bottle).  Don't use another brand, they're not worth the trouble IMO.  Take it for a long highway drive with the mixture in (a couple hundred miles would be great).  That will do a pretty good job of cleaning up the injectors and valves, and may allow you to avoid having a service station do an expensive injector cleaning job.

[DOODO0]

Thanks for the input. I really hope the tune up and cleaning the intake will help me get atleast 18 mpg, cause otherwise imma gonna have to sell her, and I already fell in love with her

[jzmtl]

You can have this done at a service station, or you can do it yourself with a can of Seafoam.  I'm not going to go over the Seafoam procedure--buy a can and read the directions if that's the route you decide to take. 

or a bottle of tap water. 

[Mike]

Take your foot off the gas pedal.

Mike

[WhichDawg]

service light (check engine light?) that's not good, you better take it in but quick and have it checked out
ask family and friends for a good mechanic, and if you just got it, the faster the better! I hope you didn't get a lemon, good luck.

[NutSAK]

You can have this done at a service station, or you can do it yourself with a can of Seafoam.  I'm not going to go over the Seafoam procedure--buy a can and read the directions if that's the route you decide to take. 

or a bottle of tap water. 

I've used that method too, but it doesn't seem to work as well as Seafoam.  It may just be my imagination though....

[NutSAK]

service light (check engine light?) that's not good, you better take it in but quick and have it checked out
ask family and friends for a good mechanic, and if you just got it, the faster the better! I hope you didn't get a lemon, good luck.

The majority of service or check engine lights are caused by faults in the emissions system.  While a fault in the emissions system can cause major issues with fuel mileage (from the computer telling the mixture to richen), it usually is not going to cause damage.

[stressmaster5000]

I don't think anyone has mentioned the air filter yet.    Did you check that? I had some road work done near my home once and all the dust caused me a clogged air filter and my v6 ford ranger went from 18mpg to 11mpg in a flash.

[Tarrodemierda]

just change it for two older v8 models made before 70´s ,man,no computers= no problems

[duckman1975]

If you don't want to part with your impala, I suggest you buy a smaller car expensive solution but with the money you will save on gas it'll pay for itself.

[Splat]

Change your air and oil filters. Re: the check engine light, that comes on at certain mileage points and is usually reset when the mechanic does his checkup.  I would bring her in and see what's what. Better to spend some $ to find out what you've got than to get stuck in the middle of nowhere because of something that may be a simple fix. Good luck.

[BIG-TARGET]

To help your gas milage, do nwhat Adam Savage and Jamie Hyneman did with a 67 Impala. Bolt a JATO to the roof

[665ae]

In addition to the regular tune-up items and having the computer scanned, at 117,000 miles, it's probably due for a cleaning out of the carbon from the intake and combustion chambers.  You can have this done at a service station, or you can do it yourself with a can of Seafoam.  I'm not going to go over the Seafoam procedure--buy a can and read the directions if that's the route you decide to take.  The service station will hook it up to a machine to do it.

Pour a bottle of Chevron Techron concentrate fuel system cleaner in the gas tank at a high cleaner/gas ratio (read the bottle).  Don't use another brand, they're not worth the trouble IMO.  Take it for a long highway drive with the mixture in (a couple hundred miles would be great).  That will do a pretty good job of cleaning up the injectors and valves, and may allow you to avoid having a service station do an expensive injector cleaning job.

That's the boring way... run her till the gas light comes on, fill it up with premium fuel, dump the injector cleaner in there, then take it out and run the hell out of it.  Pedal to the floor a few times during accelerations and open it up a bit on the highway and you'll clean it out pretty good.  Plus it's a hell of a lot of fun

I would also suggest having your exhaust/emissions system checked out.  If there's a problem with some emission components, it could affect your gas mileage quite a bit.  Having a dealer or a parts store check it with a scan tool should tell you if there's any problems.

[NutSAK]

Actually, the Seafoam and heavy foot are REALLY cool if you do them together.  The folks following you will think you just hit the smokescreen button that Q hooked up for you.   

[Mike]

Are you sure nobody is siphoning gas out of your tank? Just a thought.

Mike

[665ae]

Actually, the Seafoam and heavy foot are REALLY cool if you do them together.  The folks following you will think you just hit the smokescreen button that Q hooked up for you.   

It'll be like a real life version of Spy Hunter

[jzmtl]

When I did seafoam on mine it was quite unimpressive, barely visible smoke from exhaust. But I've seen photos where you'd think the car caught on fire, literally cloud of smoke 30 ft high.

[NutSAK]

That's good!  Your engine wasn't as packed with carbon as theirs was.  I've never seen that from my vehicles either.

I just Seafoamed the 40-year-old 289 in my Bronco a few weeks ago, and those results were unimpressive also.

[DOODO0]

I checked the air filter and it is fresh. I'm planning on doing the seafoam treatment soon and hope that will yield the results im looking for. I just also wanted to add; that when i rev the engine to 4-5 rpms the whole car starts to violently shake and just does not sound good at all. But when i floor it while driving it behaves like it should. Thanks for the help.

[specgrade]

 A lazy oxygen sensor will cause bad gas milage as will a bad coolant sensor. These will cause your check engine light to be on. Have you had the codes read yet? I believe Autozone will do it for free or you can get a code reader that plugs in under the dash.

 BTW, the seafoam/fuel injector/ oil additives/ cleaners are all wastes of money.

[NutSAK]

 BTW, the seafoam/fuel injector/ oil additives/ cleaners are all wastes of money.

I call BS on that one--I have seen the positive results of Seafoam and GM Goodwrench Top Engine Cleaner on valve and combustion chamber deposits first hand.  Water also works, but not as well.  I have also seen the results of Chevron Techron injector cleaner first hand, but none of the others have worked for me.  Oil additives are a waste of money, IMO, but they haven't been suggested in this thread.

The O2 sensor suggestion is a good one, and I would suggest changing them AFTER the Seafoam process.

[specgrade]

 BTW, the seafoam/fuel injector/ oil additives/ cleaners are all wastes of money.

I call BS on that one--I have seen the positive results of Seafoam and GM Goodwrench Top Engine Cleaner on valve and combustion chamber deposits first hand.  Water also works, but not as well.  I have also seen the results of Chevron Techron injector cleaner first hand, but none of the others have worked for me.  Oil additives are a waste of money, IMO, but they haven't been suggested in this thread.

The O2 sensor suggestion is a good one, and I would suggest changing them AFTER the Seafoam process.

 Call it what ya want, I have yet to see any proof that these products will get ya better gas mileage.

[Dtrain]

I grew up in my father's garage so here is my two cents.

1. Have the codes checked on your engine. As said before a bad O2 sensor can cause a degredation in fuel mileage.
    in some cases the engine is getting more fuel than it needs.
2. The vibration can be caused by a bad motor mount or possibly the timing sensor bieng out of wack. when you say
    4-5 rpm I hope you mean 4-5 hundred, ie idle. 4-5 thousand on the tach especially in a higher mileage car is hard
    on the engine
3. See if you can locate a garage that has the MotorVac sytem or Carbon Clean. The place I used to work for long
    before I began driving built the hose kits and sold the machine. I had my car and my wifes car done on the
    machine while the saleman demo'ed the system. Both cars at the time were running rough, even after a tune up.
    In both cases the respective dealers recommended having the injectors replaced. I had tried several pour in
    cleaners with no positive results. After having the Motorvac Sytem clean the engine My O2 senor problems and
    injection issues went away
4. Another area to check is the fuel delivery system. Change your fuel filter and have a garage do a pressure check.
    It is quite possible the rough idling is from a clogged filter or a failing fuel pump.
5. As said before though, a good tune-up can't hurt.

Good Luck

Dtrain

[Whoey]

if your impala is getting bad gas mileage try getting a new cheetah to chase it... 

[Roadie]

if your impala is getting bad gas mileage try getting a new cheetah to chase it... 

[Mike, Lord of the Spammers!]

if your impala is getting bad gas mileage try getting a new cheetah to chase it... 

[specgrade]

if your impala is getting bad gas mileage try getting a new cheetah to chase it... 

 That's the funniest thing I've heard all day...Thanks!

[NutSAK]

 BTW, the seafoam/fuel injector/ oil additives/ cleaners are all wastes of money.

I call BS on that one--I have seen the positive results of Seafoam and GM Goodwrench Top Engine Cleaner on valve and combustion chamber deposits first hand.  Water also works, but not as well.  I have also seen the results of Chevron Techron injector cleaner first hand, but none of the others have worked for me.  Oil additives are a waste of money, IMO, but they haven't been suggested in this thread.

The O2 sensor suggestion is a good one, and I would suggest changing them AFTER the Seafoam process.

 Call it what ya want, I have yet to see any proof that these products will get ya better gas mileage.

Come over to my garage sometime, and I'll show you proof while we drink a couple of beers.    That is, if you agree with the fact that cleaner valves result in a more efficient engine.