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Unread 06-21-2011, 09:22 PM   #16
roertw006
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2004 KJ Liberty 
 
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Quote:
Originally Posted by Reptile View Post
Well, actually yes heavy foot is going to have a huge impact.
Yes, I agree, but not a big enough impact to be completely responsible for 12MPG. There MUST be something mechanical/electric going on.

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Unread 06-21-2011, 09:43 PM   #17
Reptile
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1991 XJ Cherokee 
 
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Check the few things I've mentionned. I can tell you they work from experience with this vehicle. Add to that the air filter...
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Unread 06-21-2011, 09:49 PM   #18
roertw006
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Quote:
Originally Posted by Reptile View Post
Check the following:
- do battery cables/connectors show signs of corrosion?
- check for any vacuum leaks, cracked hoses under the hood
- finally, you might want to consider replacing your crankshaft and cam position sensors.

Is your engine light on?
I'll give the hoses a check, although I can't imagine they would cause a decrease in MPG. I have no clue how to go about all this crankshaft/cam position sensor business.

the battery cables are fine, no corrosion, and that wouldn't affect MPG anyway.
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Unread 06-21-2011, 10:26 PM   #19
Reptile
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The sensors are located under the engine. Easy to replace, just a little challenging to see where they're at.

Look at the hoses connected to the air filter box. Cracks even small are no good. There are sensors that measure air pressure in the engine that will affect the fuel mixture.

The ECU is entirely dependent on the battery. Tiny fluctuations in voltage can affect the ECU, which in turn can affect performance and MPG (the ECU controls everything from air/fuel mixture ratio to advance at ignition).
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Unread 06-22-2011, 06:47 AM   #20
tbmatthews82
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2007 WK 
 
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As stated before, next thing I'd do is a T-Case fluid change, Tranny filter/fluid change, and rear diff fluid change. Then disconnect the battery overnight, and start out fresh in the morning.

And please don't take it somewhere to get those things done. You'll get raped for no reason. They're very easy, and shouldn't take you longer than a Saturday afternoon.
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Unread 06-22-2011, 06:41 PM   #21
Reptile
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Quote:
Originally Posted by tbmatthews82 View Post
As stated before, next thing I'd do is a T-Case fluid change, Tranny filter/fluid change, and rear diff fluid change. Then disconnect the battery overnight, and start out fresh in the morning.

And please don't take it somewhere to get those things done. You'll get raped for no reason. They're very easy, and shouldn't take you longer than a Saturday afternoon.
You'll get ****ed in the *** with no lubrication, I agree.

Yes, clogged filter (tranny or engine oil) can possibly have an impact. It makes the engine run harder cause the flow is restricted.

Also, did you start running the AC? An excessively overcharged system will put an extra load on the engine.
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Unread 06-25-2011, 01:23 AM   #22
roertw006
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Quote:
Originally Posted by tbmatthews82 View Post
As stated before, next thing I'd do is a T-Case fluid change, Tranny filter/fluid change, and rear diff fluid change. Then disconnect the battery overnight, and start out fresh in the morning.

And please don't take it somewhere to get those things done. You'll get raped for no reason. They're very easy, and shouldn't take you longer than a Saturday afternoon.
nope, i never take it to a dealer/repair shop. most things can easily be done at home, including all the changing of fluids as was mentioned earlier. it has had a recent oil change/oil filter change. other than that, no maintenance has happened that should effect the performance(other than the spark plug change i mentioned earlier). i am going to give all the fluids a change; they all have more miles on them than they should. also, i just got my OBDII in today and pulled up a P2302 error code. according to the haynes manual, thats a problem with the #1 ignition coil. im pulling it out to inspect tomorrow. hopefully it can be fixed with a simple clean job or at most a replacement part.
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Unread 06-25-2011, 03:16 AM   #23
LibertyTC
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Best you can do is keep it in tune, clean the IAC and TPS & ports as well.
I run Mobil 1 syn 5w-30 and get about 22 on highway.
Lets face it this is not a light jap compact crap box.
Now enjoy the safe KJ drive &....
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Unread 06-25-2011, 10:40 PM   #24
roertw006
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Quote:
Originally Posted by LibertyTC View Post
Best you can do is keep it in tune, clean the IAC and TPS & ports as well.
I run Mobil 1 syn 5w-30 and get about 22 on highway.
Lets face it this is not a light jap compact crap box.
Now enjoy the safe KJ drive &....
id be overjoyed to get 22MPG on the highway. best ive ever gotten was 21MPG with a tailwind. how do i go about cleaning the IAC and TPS?

also, how do i troubleshoot the P2302 code(ignition coil #1--secondary circuit)? i checked secondary resistance and my cheapo multimeter must be garbage because it didnt show any resistance on the one in question or the one i took of as a control.
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Unread 06-26-2011, 06:28 AM   #25
tbmatthews82
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Was your CEL on?
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Unread 06-26-2011, 06:30 AM   #26
tbmatthews82
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I'd replace the #1 ignition coil completely and see what that does. At your age/mileage, it's completely normal to have one go bad.
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Unread 06-27-2011, 11:19 AM   #27
d5332
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Getting 24mpg when cruising at 55…

Getting 22mpg when cruising at 70…

Getting 16 in City….

Why is this significant to me…because we were getting 12mpg in City and 14-15 in highway…

What did I do…began working on the Jeep myself and becoming very familiar with it…

I know the Tach is not 100% accurate but if there is a change on averages then there is a change on on mpg for sure….

What did I do to tune it up?

Replaced cracked vacuum hoses, replacement cost was less than $10 bucks….Dealership however wanted hundreds upon hundreds of dollars, you see the Jeep was periodically shutting off….Dealership said I needed a whole bunch of parts replaced…I fixed the shutting off problem by using duct tape and electrical tape on the hoses but I finally replaced them.

I put new plugs in and cleaned the throttle…

Replaced the Idle Air Control Valve bc it was rough, valve was clogged with Carbon…

Most importantly I replaced the 2 pre-cat O2 sensors myself. This I think was what made the difference…

In the past I paid to have both sensors replaced, I was charged 80.00 per sensor plus installation. I was told the sensors had to come from the dealership only.

I purchased the 02 sensors myself last week to replace them once again. To my surprise, the 02 sensors that I paid a mechanic for are NOT Mopar/NTK OEM. They are $30 garbage sensors, not even Bosch…

One sensor went dead completely, engine code P0135, the other sensor must have been on its way out as well….

I put two NTK sensors in it and I don’t know yet how much of a diff it will really be but the Tach is putting out averages that I am looking forward to….

Moral of the story buy your own parts and have them installed and wait while the car is fixed or just do the repairs yourself.
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Unread 06-27-2011, 11:20 AM   #28
d5332
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forgot to mention I poured 3 bottles of Techron in the gas tank in the past week....
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Unread 08-07-2011, 09:51 PM   #29
mwne2nks
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I just checked mine after a KC run. 23 MPG at 75 for most of the trip. I'm pretty happy after reading some of these lower reports.
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Unread 08-08-2011, 01:16 AM   #30
patter5
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Quote:
Originally Posted by mwne2nks View Post
I just checked mine after a KC run. 23 MPG at 75 for most of the trip. I'm pretty happy after reading some of these lower reports.
23mpg i only get 15
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