please help MPG significantly lowered - Chevy Impala Forums

It appears you have not yet registered with our community. To register please click here...

Chevy Impala Forums

Go Back   Chevy Impala Forums > Performance and Technical > Chevy Impala 7th Gen Discussion

Chevy Impala 7th Gen Discussion W-Body 2000-2005. Discuss all Chevy Impala 7th Generation Performance and Technical Discussion here.

Reply
 
LinkBack Thread Tools Display Modes
Old 07-12-2012, 07:54 PM   #1 (permalink)
Member
 
05_impala's Avatar
 
Join Date: Nov 2009
Posts: 34
Thanks: 0
Thanked 0 Times in 0 Posts
Angry please help MPG significantly lowered

hey guys i been lurking the forums for a while. i own a 05 impala its a good car and does good on gas. i was getting 330 miles on a tank on average. well here is the problem, within the last 2 weeks my impala has lost 130 miles of driving range. im basically driving a truck thats how bad it is. i have to fill up every 200 milesbelow is a list of what i thought it could be.

1.a bad cat i just had it changed this week and was also having a exhaust leak. it was in the flange so i got both of those taken care off. still bad gas does run a lot better tho and i dont feel the heat of the engine anymore when i open the doors. also not as loud

2. O2 sensor i got the car scanned at o reilys . i was told it was going bad , the one closer to the manifold. if this was the problem what tools would i need to replace it and what would be a good brand ?

3. a tune up, i say this cause the car has 177,000 miles on it and i never had a tune up . i done a bit of research and figured ac delco is the most mentioned on this site . same for the wires but not sure what type of wires i would need.

4. temp sensor / thermostat when i had the car scanned it said thermostat and temp sensor. i have a thermostat just havent put it in yet. i was going to tackle the temp sensor while putting on a new thermostat since they're both close .

i cant think of anything else that could cause this . i used gas from QT by my house and i used it when the QT was brand new. on that one tank i experienced the mpg decline. i thought it was bad gas but then on the next tank it was still not doing good. i filled up using exxon and a bottle of seafoam injector cleaner not a difference. i was really hoping a changed cat would've solved this.

05_impala is offline   Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Old 07-12-2012, 08:00 PM   #2 (permalink)
Senior Member
 
csawyer's Avatar
 
Join Date: Apr 2012
Location: Charleston, SC
Posts: 418
Thanks: 0
Thanked 2 Times in 2 Posts
I would most definitely go through your list of items and replace them all. With that kind of mileage on the car, you won't hurt anything and may fix the problem. You might also check your fuel pump and filters. Fuel, air, & spark are the 3 things you need to make sure you have enough of to get things running properly. If you eliminate those issues, then it's time to have someone dig deeper.

__________________
Sawyer
"Never drive faster than your guardian angel can fly!"
csawyer is offline   Reply With Quote Quick reply to this message
Old 07-12-2012, 08:38 PM   #3 (permalink)
Member
 
05_impala's Avatar
 
Join Date: Nov 2009
Posts: 34
Thanks: 0
Thanked 0 Times in 0 Posts
yea i was going to do all that. i just need to get that gas problem fixed. i plan on doing a tune up within the next week or two. depending on how soon i can get my normal mpg back.

05_impala is offline   Reply With Quote Quick reply to this message
Old 07-12-2012, 08:40 PM   #4 (permalink)
Divine Autosound
 
C.E.Divine's Avatar
 
Join Date: Aug 2011
Location: Fayetteville, AR
Posts: 2,168
Thanks: 0
Thanked 9 Times in 9 Posts
Get that o2 sensor swapped out. Go factory for that one as well. Stay away from Bosch. Soak the old one with pb blaster or liquid wrench the night before you go to do the work. You will want to use a crows foot socket on it, since a normal closed end wrench may not be big enough to fit the connector through over the wires. And DO NOT use an open end wrench. You will round off the sensor, and that will leave you in a world of hurt. Crows foot is the way to go. The reason you need to get that changed is because the o2 sensor going bad will nearly always cause the car to run rich, and all of the unburned fuel will plug up the cat. That may be what did your old one in, and if you don't change that sensor, it could screw up your new one as well.

Go ahead with the tune up as well. If those are factory spark plugs, they are definitely part of the problem for sure. I bet once you change those, it will feel like a brand new car power wise.

To bring a point to what csawyer said earlier about fuel filter, the fuel filter is non serviceable. It is part of the fuel pump assembly. So check your fuel pressure, and if it is low, you need a whole new pump. Stick with factory once again, and like I said before, stay away from Bosch (do you notice a trend here? Most Bosch stuff is total crap.) stay away from airtex as well. If you get one of the airtex pumps, you will be doing the job again in a year or less. Go with the oem Delphi pump.

C.E.Divine is offline   Reply With Quote Quick reply to this message
Old 07-12-2012, 09:07 PM   #5 (permalink)
Member
 
05_impala's Avatar
 
Join Date: Nov 2009
Posts: 34
Thanks: 0
Thanked 0 Times in 0 Posts
woah i just seen the filter the other day. lol i dont own a 8th gen lol ,yea i learned bosch is crap from lurking around here. so i figured i need a socket and a extender and one of those twisty things for the spark plugs. this maybe the crows foot you speak off. me and guy at oreilys have become best friends over the past week because of this car. lol will definitly change the wires and spark plugs. ac delco for the plugs and wires right ?

05_impala is offline   Reply With Quote Quick reply to this message
Old 07-13-2012, 05:22 AM   #6 (permalink)
Senior Member
 
jrd0304's Avatar
 
Join Date: Aug 2009
Location: Cleveland, OH
Posts: 150
Thanks: 2
Thanked 5 Times in 3 Posts
Tune up might be ok and really it's due for one, but I'm curious about what would happen if you resolved all of your MIL / trouble codes before you started disrupting the ever-so-touchiness of a high mileage engine. I've learned the hard way, at this stage in the game especially with so many miles, if you don't know 100% something is bad, don't even touch it.

If you decide to do a tuneup, replace anything you have with AC Delco if you can. Call a Chevy dealer for the most recent part numbers if need be. These discount parts stores aren't always the best place to get plug part numbers, because their computers are set up to tell you basically any plug that will screw into the head will be fine for your car, which I can tell you, is basically not the case. If you use anything but AC Delco, especially with the plugs, you may end up making it run even worse. Can you get to the upstream 02 sensor with an 02 sensor socket? I know they sometimes have them for rent at the parts store. But I wonder, if you're not getting a MIL indicator from the upstream 02, why do you think it's going bad? Is it because it's not giving you the right measurements in the datastream on the scanner? Is there a pending code? I wouldn't touch any sensor unless it's either giving you a code or a pending code, or it's not giving good readings in the datastream.

I believe your last item in the list could be worth looking into, I could be wrong of course, but read on. Your engine temperature matters to the fuel injection system. The PCM must always be getting an accurate reading from the temp sensor. If the thermostat is bad, replace that, too, or you will overcool or overheat depending if it's stuck open or closed. The engine should be running at the right temp, and providing the right temp readings to the PCM. The temp sensor works with the throttle body, PCM, and fuel injection system to provide the right lean/rich mixture of fuel to the engine. Back in the day, we used to call these chokes, but those don't exist anymore, Lol. I can't be too sure, but I think the temperature sensor tells the PCM when the car is warm, and then the PCM works with the fuel injection system to back down the richness. I'd make sure you're in closed loop mode after warm up on the scanner in the datastream - if the car is at full temp, and you're in open loop mode, then your system is isn't recognizing the engine has warmed up properly - if you're not in closed loop mode after warmup, then the engine/PCM is being tricked into thinking it's in warm up mode, and will use more gas. And, of course, if the datastream isn't reporting a temperature, then that tells you the sensor is bad, and needs replaced. Could that be part of the problem?


Last edited by jrd0304; 07-13-2012 at 05:45 AM..
jrd0304 is offline   Reply With Quote Quick reply to this message
Old 07-13-2012, 06:01 AM   #7 (permalink)
Senior Member
 
csawyer's Avatar
 
Join Date: Apr 2012
Location: Charleston, SC
Posts: 418
Thanks: 0
Thanked 2 Times in 2 Posts
^^What he said.^^ And yes, stick with AC Delco.

__________________
Sawyer
"Never drive faster than your guardian angel can fly!"
csawyer is offline   Reply With Quote Quick reply to this message
Old 07-13-2012, 06:33 AM   #8 (permalink)
Member
 
05_impala's Avatar
 
Join Date: Nov 2009
Posts: 34
Thanks: 0
Thanked 0 Times in 0 Posts
well the scanner said what Q2 sensor was bad. it was bank 1 , and im not doing the tune up yet. im just trying to get the car back to normal.

05_impala is offline   Reply With Quote Quick reply to this message
Old 07-13-2012, 06:57 AM   #9 (permalink)
Senior Member
 
jrd0304's Avatar
 
Join Date: Aug 2009
Location: Cleveland, OH
Posts: 150
Thanks: 2
Thanked 5 Times in 3 Posts
Gotcha. If you're getting a code for it, by all means do what you gotta do to replace it. To be on the safe side, when you replace the 02 sensor, replace whatever else is giving you a bad code, since it's possible that the rich condition could destroy your new 02 sensor, or result in premature failure.

jrd0304 is offline   Reply With Quote Quick reply to this message
Old 07-13-2012, 09:48 AM   #10 (permalink)
Member
 
05_impala's Avatar
 
Join Date: Nov 2009
Posts: 34
Thanks: 0
Thanked 0 Times in 0 Posts
Yea got the codes just forgot to write em down. I know you guys like the codes I'll try to get them later . I did however disconnected my battery . I bought a Bosch O2 sensor , retuned it and got a refund. So I just put a full tank in it and see if the code comes back. Hopefully the reset can get it back since the cat is 3 days old . I put 10 dollars in it and it seemed the car range was back to normal for 2 gallons . I drove to the local ac delco shop and talked about my sensor . Told him bout the bosche and he said that was a good decision . He told me the denzo and ac delco are the best for GM cars. Seen all the bad stuff bought them from here so thanks again .

05_impala is offline   Reply With Quote Quick reply to this message
Old 07-13-2012, 10:38 AM   #11 (permalink)
8th Gen Antagonist
 
kingnutin's Avatar
 
Join Date: Mar 2009
Location: Vancouver , WA
Posts: 13,656
Thanks: 516
Thanked 1,192 Times in 788 Posts
Sounds like you're getting it sorted out, but yes delco is the way to go on plugs and sensors, wires it doesn't really matter, I've never seen bad ones. 7th gens DO have a serviceable fuel filter, and the o2 sensor is best done with an o2 sensor socket.

__________________
1978 Caprice Classic Landau
350 2-bolt, stock 4bbl
Stock rebuilt TH350
Edelbrock performer cam + intake
Dual 2 1/2" Flowmaster exhuast (waiting to be installed)
Edelbrock IAS Classic shocks
95 9C1 3.08 posi
4 wheel disc brakes!
16x8 American Racing Baja's with 225/60/16 Pirelli P4's

kingnutin is offline   Reply With Quote Quick reply to this message
Old 07-13-2012, 12:34 PM   #12 (permalink)
Member
 
05_impala's Avatar
 
Join Date: Nov 2009
Posts: 34
Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by kingnutin View Post
Sounds like you're getting it sorted out, but yes delco is the way to go on plugs and sensors, wires it doesn't really matter, I've never seen bad ones. 7th gens DO have a serviceable fuel filter, and the o2 sensor is best done with an o2 sensor socket.
Yea but your input would be nice . I hope the PCM recognizes the cat change . Had to unhook battery for a while. I'll know at 40 miles if my fuel gauge moves then it hasn't been fixed .

05_impala is offline   Reply With Quote Quick reply to this message
Old 07-13-2012, 03:12 PM   #13 (permalink)
8th Gen Antagonist
 
kingnutin's Avatar
 
Join Date: Mar 2009
Location: Vancouver , WA
Posts: 13,656
Thanks: 516
Thanked 1,192 Times in 788 Posts
The PCM may not be happy with the cat change, you didn't mention what kind you used, but these are notorious for problems with aftermarket cats. A PCM tune can have the cat code removed, but you have to be willing to drop $150 on it. Still cheaper than a $400+ factory cat...

__________________
1978 Caprice Classic Landau
350 2-bolt, stock 4bbl
Stock rebuilt TH350
Edelbrock performer cam + intake
Dual 2 1/2" Flowmaster exhuast (waiting to be installed)
Edelbrock IAS Classic shocks
95 9C1 3.08 posi
4 wheel disc brakes!
16x8 American Racing Baja's with 225/60/16 Pirelli P4's

kingnutin is offline   Reply With Quote Quick reply to this message
Old 07-13-2012, 04:39 PM   #14 (permalink)
Member
 
05_impala's Avatar
 
Join Date: Nov 2009
Posts: 34
Thanks: 0
Thanked 0 Times in 0 Posts
yea its just a cat from the exhaust shop. i wanted a magnaflow hi flow but was told they didnt have good flow. i was guzzling gas with the old cat . cat was changed this week but the 14 mpg im getting has been going on for 2. had a exhaust leak in the flange and a bad converter . thought that was the reason but its still bad on gas. driven 30 miles since i unhooked the battery for reset.

05_impala is offline   Reply With Quote Quick reply to this message
Old 07-13-2012, 05:07 PM   #15 (permalink)
8th Gen Antagonist
 
kingnutin's Avatar
 
Join Date: Mar 2009
Location: Vancouver , WA
Posts: 13,656
Thanks: 516
Thanked 1,192 Times in 788 Posts
Get that upstream o2 sensor changed, the fuel filter changed, and the tune-up done. See how it is after that. It is most likely the o2 sensor though, from what you've told us.

__________________
1978 Caprice Classic Landau
350 2-bolt, stock 4bbl
Stock rebuilt TH350
Edelbrock performer cam + intake
Dual 2 1/2" Flowmaster exhuast (waiting to be installed)
Edelbrock IAS Classic shocks
95 9C1 3.08 posi
4 wheel disc brakes!
16x8 American Racing Baja's with 225/60/16 Pirelli P4's

kingnutin is offline   Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Reply


Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Chevy Impala Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools
Display Modes

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Lowered 63 4 Door??? Olbeedo Chevy Impala Discussion 2 07-10-2012 07:01 AM
lowered my 94, pictures, and a couple of questions bad25v8 Chevy Caprice 2 06-09-2011 10:47 PM
Any lowered '77 to '90? 77LedSled Appearance 2 04-02-2011 08:35 PM
Lifting A Lowered Car badcompany87 Autocare and Maintenance 9 10-31-2009 02:08 PM
Lowered with 20's installed for the summer wedebrook Chevy Impala 7th Gen Discussion 13 03-28-2009 07:57 AM




Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Search Engine Friendly URLs by vBSEO 3.6.0 ©2011, Crawlability, Inc.
This site is not affiliated nor endorsed by General Motors Corp. Chevy Impala and related trademarks are the property of General Motors Corp.