2005 jeep Grand Cherokee V8 4.7 poor gas mileage

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  #1  
Old 11-18-10, 09:05 AM
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2005 jeep Grand Cherokee V8 4.7 poor gas mileage

I have experienced a drop in mileage over the past number of months which I have confirm by manual tracking. A tune up has not changed problem. Diagnostics show on problems- the car seems to be running just fine! (other than noted mileage)
If I set on board mileage tracking and use the cruise and reset avg on the dash I get normal mileage???
This would seem like a electrical problem??
any help or thoughts.
Maybe does this seem to be the first such case nobody has been of any help. YET>
Thanks
 
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  #2  
Old 11-18-10, 10:22 AM
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How big a drop in average mileage? Doing the same type of driving everyday? Vehicle mileage?
 
  #3  
Old 11-18-10, 10:36 AM
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pretty much, drop of 7-8 miles city driving is the biggest about 9-10. If i can use cruise 15.7 -17.5
 
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Old 11-18-10, 03:29 PM
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I also believe the Grand Cherokee V8 has been rated the worst in fuel economy. It's only rated at like 13 city and 18 highway, so........

Bad O2 sensors, catalytic converter, etc are things that can significantly decrease mileage.
 
  #5  
Old 11-18-10, 04:31 PM
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Thanks for the input ,I had Diagnostics run which had no problems at all wouldn't those show as a error code? Actually i was getting a little better 15.5 -17 city 20.5 -22 highway I use cruise allot for both when I can.
 
  #6  
Old 11-19-10, 04:52 AM
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Start using a good quality “Top Tier” fuel. Clean the fuel injectors using the “On The Car” method. Shop around for a shop in your area that cleans fuel injectors with the tools in the links below. Don’t waste your time or money with ANY product that gets poured into the fuel tank. They are all “BS” and a waste of money.

http://www.wynnsusa.com/pdf/14241_ENVIRO_SpecSheet.pdf

BG Company

OTC Tools OTC 7659 - Fuel Injector Cleaning Kit
 
  #7  
Old 11-19-10, 05:32 AM
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Again thank you...I'll shop my area for this service what is the cost I should expect to pay? Also top tier fuel do you mean shell or sunoco? I do not not use no name off brands gas. thought I have seen the no name tankers at all gas stations.
 
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Old 11-19-10, 07:04 AM
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Stay away from ethenol based fuels (it should say on the pumps whether or not it's ethenol based, in most states). Get 100% gasoline. The little extra money it costs will be offset by the MPG increase.
 
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Old 11-19-10, 09:16 AM
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You're welcome,

(Question) Also top tier fuel do you mean shell or sunoco?


TOP TIER Gasoline Retailers:

76 Petro-Canada
Aloha Petroleum Phillips 66
Chevron
Chevron QuikTrip
Chevron Canada Rebel Oil
Conoco Road Ranger
CountryMark Severson Oil
Entec Stations Shell
Esso
Shell
Shell Canada
Exxon
Sunoco
Sunoco Canada
Kwik Trip / Kwik Star Texaco
MFA Oil Co. The Somerset Refinery, Inc.
Mileage Stations Tri-Par Oil Co.
Mobil Turkey Hill Minit Markets
U.S. Oil
 
  #10  
Old 11-19-10, 09:29 AM
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check to see if your thermostat is working properly this will give poor fuel economy if it dosent come up to proper operating temp also possible temp sensor might be out of range.
 
  #11  
Old 11-19-10, 09:33 AM
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you know jeep cherokees are notorious for plugged converters as well, vacuum or back pressure testing will quickly show an issue.
 
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Old 11-19-10, 11:32 AM
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(Quote) check to see if your thermostat is working properly

(Quote) you know jeep cherokees are notorious for plugged converters as well, vacuum or back pressure

It’s extremely rare for the above to occur in a setting that (doesn’t present) with drivability or performance issues.

Those include:

Backfiring
Hesitation
Rough idle
Misfires
Stalling
Hard starts, either on a hot, cold, or warm engine
The setting of error codes


Which if (any) apply to you?
 
  #13  
Old 11-19-10, 05:55 PM
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Originally Posted by HotinOKC View Post
Stay away from ethenol based fuels (it should say on the pumps whether or not it's ethenol based, in most states). Get 100% gasoline. The little extra money it costs will be offset by the MPG increase.
But THEN what? Have to rely on that much more foreign oil? Isn't part of the ethanol plan our ability to gain some energy independence?

Or is it a folly, from the standpoint that if enthanol wastes mpg, that we are no further ahead in that regard(foreign oil reliance)? So, basically we are doing it to help support the farmer?
 
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Old 11-20-10, 09:27 AM
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Energy independence will never happen. Ethanol is just a gimmick. Just look what ethanol does to small engines like lawn mowers and weed eaters. They have been preaching corn based ethanol only because the corrupt corporate farmers want it. Next thing you know we will continue to have long droughts which will hurt the crops and we will rely on foreign suppliers just like we do now.
 
  #15  
Old 12-06-10, 07:31 AM
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No ethanol gas, thermostat is working properly
no problems with:
Backfiring
Hesitation
Rough idle
Misfires
Stalling
Hard starts, either on a hot, cold, or warm engine
The setting of error codes
I"M AT A LOST WHAT TO DO??
 
  #16  
Old 12-06-10, 08:33 PM
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If it happened all of a sudden,, What are the chances of a brake hanging on?? Is there a pull to one side or any vibration??? May be worth checking,,, Just thoughts,,Roger
 
  #17  
Old 12-07-10, 08:10 AM
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Thanks Roger
already checked this out......that was one of my first thoughts.
Thanks you for your feedback all ideas are helpful
 
  #18  
Old 12-07-10, 09:24 AM
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Assuming that your tire pressures are correct and you have a clean air filter, and the fact that you haven't mentioned any obvious front end alignment issues, the only thing that I can think of still at this point is to consider having your fuel injectors cleaned 'on the car'. This was mentioned a few threads back but with your vehicle's mileage it could still be something to consider. If it works for you and brings your mileage back up the payback might be there. You don't have any teenagers siphoning out gas, or taking your car on secret joy rides do you? I had to ask because I remember doing that as a teenager until I got caught but that is probably another forum.
 
  #19  
Old 12-07-10, 10:12 AM
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I have run injector cleaners through the gas twice.Have not been able to find anyone who does OTC Tools OTC 7659 - Fuel Injector Cleaning Kit or thinks it's any better than additives?
Front end, tires etc show no issues.
I thought of the same thing about siphoning out gas and purchased a locking gas cap three weeks ago ...WITH NO CHANGE IN MILEAGE

At this point I have invested $200 -$300 in diagnostics,driveablity expert tests front-end checked brakes with no payback
I,m considering having a vacuum leak check done THIS HAS CONSUMED ME NOW
Thanks you for your feedback
 
  #20  
Old 12-09-10, 01:50 PM
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We Had The Same Problem

A customer of ours had the same problem on the same type of Jeep a few months ago. We never could find the source of the problem
 
  #21  
Old 12-10-10, 05:27 AM
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leaaseman thank you for the feedback
I think the air filter being used maybe the issue (new at time late September). I have switched brands and at this point there seems to be a improvement. A little to early to tell yet.The erratic behavior has stopped. The average MPG on dash shows better I'll do a manual check to prove this out.

Thanks you for your feedback all ideas are helpful
 
  #22  
Old 12-10-10, 08:39 AM
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Just a thought that if the recent air filter was not helpful for your gas mileage what about the plugs that were installed in September? OEM recommended plugs or other?
 
  #23  
Old 12-10-10, 09:16 AM
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thanks equinox
Yes,OEM recommended plugs,PVC,oil change and diagnostics at the same time. I did consider the others type plugs dual core, platinum etc.
The filter was still clean & white little dirt. What made me look at the filter was just troubleshooting to recheck the known and verity.Also the brand was not one I had ever used.I never heard of any problems from filter to filter? When I remove the filter then drove the car (a little 50 miles) is when I noticed the apparent change in gas mileage about 7% on the average MPG.So I gassed up again improve mileage over the last check this was old filter and new on that total. DOING A MANUAL CHECK NOW with the new filter......
your feedback all ideas are helpful
 
  #24  
Old 01-06-11, 08:27 AM
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after replacing the new air filter then checking gas mileage my gas MPG is back!!!ALL FILTERS ARE NOT CREATED EQUAL

Thanks to all who give there feedback
 
  #25  
Old 01-06-11, 08:45 AM
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Well...in case I missed it in the earlier posts...what brand was giving you a problem?
 
  #26  
Old 01-06-11, 09:38 AM
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2005 jeep Grand Cherokee V8 4.7 poor gas mileage

Gunguy45
no advertising whether it is positive or negative I guess that was never mention?

CAR-QUEST
 
  #27  
Old 01-06-11, 10:05 AM
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Posting purely to bash or promote a product is never allowed, but commenting on a problem a particular item gave in your issue is ok.

Just like when our Pro mechs say always use xxx brand with a xxx vehicle to avoid issues.
 
  #28  
Old 01-07-11, 06:41 PM
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Originally Posted by dagresta View Post
pretty much, drop of 7-8 miles city driving is the biggest about 9-10. If i can use cruise 15.7 -17.5
let me surprise you. you are, actually, about right on the mpg for that vehicle.

Search by Manufacturer


your s is said to be 13 to 18, city to hwy. that's a for a new car. now, deduct mileage, years of use, WINTER *******ED GAS FORMULATION AND 10% GASOHOL - and you'll arrive at what others average - 9 to 13 mpg.
so, that fyi, before you spend another few grand on useless repairs of upgrades and things of this nature.

hey, got to fix this. i pulled 5.7L engine. yours is about a mile per gallon better.
Average based on 6 vehicles.

16.7

Lo 15 arrow Hi 20


Fuel Economics

Cost to Drive 25 Miles

$5.12
Fuel to Drive 25 Miles

1.67 gal

Cost of a Fill-up

$57.47

Miles on a Tank

281 miles

Tank Size

20.8 gal

Annual Fuel Cost*

$3072

so, still, for a five year old car, times gasohol, times winter formulation - you are not that much behind what it is supposed to be.
 

Last edited by ukrbyk; 01-07-11 at 06:57 PM.
  #29  
Old 01-08-11, 06:36 AM
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Sorry if I wasn't very clear in that post. 15.7 - 17.5 use to be my city. It dropped to 7 - 11 city this started in the summer.
I now get 16.7 city 20.8 highway with filter change. Three x tracking manual miles/gallons
Thanks for your feedback
 
  #30  
Old 01-08-11, 08:43 AM
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very good. yeah, if it happened summer time..
my mpg dropped over one week, on my TCH, from 42 to 37. pretty positive, it was when they switched to the infamous winter formulation. also, temp-s dropped down almost over period of couple days.
i sort of panicked and asked in TCH forum, what's up with 5 mpg drop. seasoned users said - no worries, it does this. it'll pop back up late spring right away. when it warms up and they switch back to summer gas.

glad you had it soved.
 
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