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  #1  
Old 02-04-2015, 07:00 PM
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Question 11.0 mpg ?!!

OK gurus and Jeep Grand Cherokee magician's I have a 2000 JGC Limited 4.7 v8 Select Track 166.5k miles and runs great very comfortable, love it. But the gas mileage sucks. It is turning 2400 rpm @ 70 mph which to me is high. I am going Friday to the local dealer to see if the TSB for the transmission has been done, if not I will get it done if possible to change the 4 speed to a 5 and help the gas mileage. I am also chasing the demons of rear brake light troubles. Anyone have any other ideas I can pursue. Going on a trip Monday so will have a chance to give it a good 5 hour run. Thanks

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  #2  
Old 02-04-2015, 07:12 PM
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Re: 11.0 mpg ?!!

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Originally Posted by thompsb2 View Post
OK gurus and Jeep Grand Cherokee magician's I have a 2000 JGC Limited 4.7 v8 Select Track 166.5k miles and runs great very comfortable, love it. But the gas mileage sucks. It is turning 2400 rpm @ 70 mph which to me is high. I am going Friday to the local dealer to see if the TSB for the transmission has been done, if not I will get it done if possible to change the 4 speed to a 5 and help the gas mileage. I am also chasing the demons of rear brake light troubles. Anyone have any other ideas I can pursue. Going on a trip Monday so will have a chance to give it a good 5 hour run. Thanks
Your o2 sensors (you have 4) may have enough carbon build-up to affect mileage but not enough to throw the code. On my '02 4.7 HO I did this regularly by spraying contact cleaner, the kind that evaps instantly, on the cylindrical screen to clean the black carbon off. I use anti-seize on the threads when re-installing.
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Old 02-04-2015, 08:26 PM
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Re: 11.0 mpg ?!!

Thanks for the reply I will check that out. Do you know anything about TSB 18-025-01. From what I understand this will change my trans from 4 speed to 5 speed and maybe some other improvements to help gas mileage.
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Old 02-04-2015, 08:45 PM
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Re: 11.0 mpg ?!!

The O2 sensors get lazy over time and there is in fact not a good way to clean them, since the sensing element sits inside the metal perforated shell. Check them using a scanner which shows live data. The 1-1 and 2-1 sensors (upstream)should change voltage frequently from 0.2 to 0.8 V. If they donīt , then its most probably time for new sensors. The 1-2 and 2-2 sensors are behind the cats and are more used for cat performance measurements. Their voltage is more or less stable. Bad milage can have several other reasons as well, but the O2 for sure is a good point to start. Also low fuel pressure at the rail, a bad MAP sensor or even worn plugs or dirty air filter will reduce the mpg.
TSB 18-025-01 will indeed add an extra overdrive gear, 5th gear. It will reduce the noise and increase mpg (will run approx 2000 rpm at 70 mph) and it will change the shift schedule a bit.
Rear brake light problems are also a well known problem on the WJ. The solution is or bending the small copper tabs from the light socket a bit out, or doing the same with the corresponding metal contact on the light housing board. Bad contact is the problem here. Ofcourse always check the light bulb first.
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Old 02-05-2015, 02:05 AM
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Re: 11.0 mpg ?!!

I have looked at the tail lights and see no damage as far as overheating or cracking. I cleaned the contacts and they are working now, if they fail again I will take further action and may replace with LED's. What I don't understand is why they are failing only when the head lights and running lights are on. It seems if the contact is the issue they would also not work with the headlights off?
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Old 02-05-2015, 03:05 AM
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Re: 11.0 mpg ?!!

Hi all I have a Jeep Cherokee Liberty 2005 model and shows me code p0700, p0733 Is it possible to help me because lime stops at 2 parts just does not work
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Old 02-05-2015, 04:43 AM
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Re: 11.0 mpg ?!!

Quote:
Originally Posted by ahmednasser9596 View Post
Hi all I have a Jeep Cherokee Liberty 2005 model and shows me code p0700, p0733 Is it possible to help me because lime stops at 2 parts just does not work
You are now in the WJ section, your jeep is a KJ, and you can better open a new thread regarding your problem. But as a first help, the P0700 code means that the PCM (powertrain control module)has seen that the TCM (transmission control module) has set a fault code. The P0733 means incorrect gear ratio in 3rd gear, which normally means a slipping clutch in 3rd gear.
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Old 02-05-2015, 04:56 AM
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Re: 11.0 mpg ?!!

Quote:
Originally Posted by thompsb2 View Post
I have looked at the tail lights and see no damage as far as overheating or cracking. I cleaned the contacts and they are working now, if they fail again I will take further action and may replace with LED's. What I don't understand is why they are failing only when the head lights and running lights are on. It seems if the contact is the issue they would also not work with the headlights off?
I didnīt look into it for the why question. But it actually always happens with the headlights on. Both tail light and brake light use the same ground tab. It has something to do with too high of a resistance at the tab, but why it extinguishes both lamps i also donīt know.
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Old 02-06-2015, 06:42 PM
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Re: 11.0 mpg ?!!

Okay I took my jeep to the dealership today to see about TSB 18-025-01 for my 2000 JGC Limited. I was told this TSB would not improve my gas mileage or give the tranny a 5th gear, this is contrary to what I have read here and other places. Can anyone help me find the truth of this.
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  #10  
Old 02-06-2015, 07:44 PM
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Re: 11.0 mpg ?!!

I just checked the TSB and TSB 18-025-01 will add the 5th gear to the 45RFE, making it a 5-45RFE. There are some shift improvements as well, but due to the 5th gear noise will be reduced and MPG goes up. If the stealer tells you that it will not improve the mpg, look for a new stealer.
Look here for the TSB: http://www.wjjeeps.com/tsb/tsb_wj_1802501.pdf
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  #11  
Old 02-07-2015, 10:53 AM
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Re: 11.0 mpg ?!!

This really tics me off, the service manager either doesn't know his Jeeps or he doesn't want to be bothered with someone with the older models. My wife and I choose to drive the older cars because we don't want make car payments and the older cars like the JGC I have are more than capable of doing everything we ask them to do if they are taken care of.
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Old 02-07-2015, 12:31 PM
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Re: 11.0 mpg ?!!

You can just print out the TSB and show it to him. There is not written on the TSB that mpg will go up, but it mentiones that an extra final gear will be created for 99 and 00 jeeps (page 2 upper note).
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