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Mileage question
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=73926		 Page 1 of 2
Author:  thermorex [ Sun Jan 27, 2013 7:16 pm ]
Post subject:  Mileage question
Hey folks,

Quick question for you all: I changed the map sensor with a new one and I also replaced the turbo hoses with new samco. I have a 2005 crd with provent, suncoast, Kennedy lift pump. No power chips (planning on doing gde soon ). I have about 120k miles on board. When I got the jeep it had 78k, I had constant 21 mpg city and 27-30 hwy. after I hit 100, my mileage decreased to 20/city and 21/hwy. I have to also mentioned that I run with the orm (maf unplugged) and I changed the tires to offroad bf Goodrich all terrain 245/70/16 and I added a bull bar and the mopar light bar and roof rack. The 20/21 mpg was with all those installed, but less samco and new map). After changing cac hoses with samco and the map sensor with a new one, my mileage is 19 hwy. the engine seems to run ("ear-wise" and "throttle-wise") like before. I tend to believe that the poor mpg is due to winter weather and maybe different diesel. I also have 40 psi in the tires.

My question is: what do you think can cause this bad mileage? Coincidence or something else?
Author:  woodtick [ Sun Jan 27, 2013 7:43 pm ]
Post subject:  Re: Mileage question
Welcome.

1.First thing I would look at is your temp gauge. If its not at one tick left of high noon, thermostat is shot. Low engine temp will cause lower mpg.

2. pull the relay for the viscous heater. if its particularly cold and/ or t-stat is shot it will run alot.

3. check your service log. When is the last time air filter and fuel filter were changed?

4. Winter diesel sucks and causes mpg drop. This will vary depending on how crappy the winter blend your buying is.

5. Front brakes are known to drag. I pulled the caliper pins on mine and threw away this rubber spacer on the pin (not the dustboots) , cleaned, greased and that helped alot.

I have no lift (yet), or rack (yet), do have a/t tires, but even on winter blend in the city I get 20-21 Hwy 27-30 by doing these things. My :2cents:
Author:  kjjet [ Sun Jan 27, 2013 8:04 pm ]
Post subject:  Re: Mileage question
thermorex wrote:
Hey folks,

Quick question for you all: I changed the map sensor with a new one and I also replaced the turbo hoses with new samco. I have a 2005 crd with provent, suncoast, Kennedy lift pump. No power chips (planning on doing gde soon ). I have about 120k miles on board. When I got the jeep it had 78k, I had constant 21 mpg city and 27-30 hwy. after I hit 100, my mileage decreased to 20/city and 21/hwy. I have to also mentioned that I run with the orm (maf unplugged) and I changed the tires to offroad bf Goodrich all terrain 245/70/16 and I added a bull bar and the mopar light bar and roof rack. The 20/21 mpg was with all those installed, but less samco and new map). After changing cac hoses with samco and the map sensor with a new one, my mileage is 19 hwy. the engine seems to run ("ear-wise" and "throttle-wise") like before. I tend to believe that the poor mpg is due to winter weather and maybe different diesel. I also have 40 psi in the tires.

My question is: what do you think can cause this bad mileage? Coincidence or something else?



19 on the highway is not very good, unless you are going 85 mph? Winter Diesel? may be some of it. Woodtick gave you good advice to check.

@120K If you still have poor mileage, you may be having symptoms of worn rockers. The valves may not be opening enough to effectively produce all the power.
Author:  thermorex [ Sun Jan 27, 2013 8:54 pm ]
Post subject:  Re: Mileage question
woodtick and kjjet,

Thanks for suggestions! My tstat was changed about 15k miles ago with a new one (old was blocked on semi-open). The temp is a tick to the left, where it should be. I will check if breaks are hot, but about 30k miles ago, when I changed the pads I used some anti-seize on the pins and where the pads sit on the caliper. Won't hurt to double check again, maybe even re-service them again, clean and use some silicone grease. I'll also look at the viscous relay per suggestions. Regarding the rockers, I hope it's not that, they don't have any funny sounds (those typical tics when the distance gets messed up and they need to be setup again) but I'll look at that also. Also, at little less than 100k I changed tbelt and all the pulleys, including those on the serpentine. All parts that I used are mopar.

Thanks again for the tips, if anybody has more, I'd appreciate them.

Edit: speed that I got 19 mpg was in between 75 and 78, with small exceptions due to the traffic. I drove a little over 700 miles. Fuel filter and oil+filter was changed right before the trip. K&n filter I use had been also cleaned same day I did oil and dsl filter.
Author:  woodtick [ Sun Jan 27, 2013 9:12 pm ]
Post subject:  Re: Mileage question
[quote=" speed that I got 19 mpg was in between 75 and 78, with small exceptions due to the traffic. [/quote]

Slow down to 68 and I'll bet you'll top 26 hwy. 1800 rpm seems to be the "sweet spot" but 2k rpm or less is where the efficiency lies.

With regard to brakes, to check if they are dragging, hoist the front tires and spin by hand. You will be able to tell if they are dragging. If they are, pull the caliper pins. One on each side will have a rubber sleeve on it. Cut it off, clean, grease with marine grade grease and reassemble to cure drag. Do not cut or discard dust boots.
Author:  thermorex [ Sun Jan 27, 2013 9:22 pm ]
Post subject:  Re: Mileage question
Woodtick,

Will do. In fact it easier to lift a front side and spin the wheel rather than check if wheel is hot. I'll definitely cut out the rubber sleeve. Definitely wont take out dust boots even if you want to, lol. I'll give it a shot again at 1800 rpm and see what's the mileage. Thing is that when you drive 700+ miles at once its hard to go that slow, but at least it's worth to see what mileage I get like that. I usually stay under 2300 rpm. I think at 80 mph I have about 2400 rpm, maybe a little less.

Again, thanks a lot!
Author:  kjjet [ Sun Jan 27, 2013 10:09 pm ]
Post subject:  Re: Mileage question
[quote="thermorex"]woodtick and kjjet,

Regarding the rockers, I hope it's not that, they don't have any funny sounds (those typical tics when the distance gets messed up and they need to be setup again) but I'll look at that also. Also, at little less than 100k I changed tbelt and all the pulleys, including those on the serpentine. All parts that I used are mopar.

The CRD uses hyd lifters which take up any gap worn rockers may have, so there will not be any noise differance. i had rocker failure with no noise or warning.

I hope you dont, but lots have.

Good luck.
Author:  thermorex [ Sun Jan 27, 2013 10:15 pm ]
Post subject:  Re: Mileage question
kjjet wrote:
thermorex wrote:
woodtick and kjjet,

Regarding the rockers, I hope it's not that, they don't have any funny sounds (those typical tics when the distance gets messed up and they need to be setup again) but I'll look at that also. Also, at little less than 100k I changed tbelt and all the pulleys, including those on the serpentine. All parts that I used are mopar.

The CRD uses hyd lifters which take up any gap worn rockers may have, so there will not be any noise differance. i had rocker failure with no noise or warning.

I hope you dont, but lots have.

Good luck.


Thanks, didn't know they have hydraulic rockers. At least is good (in a way) they don't have the Vw/Audi type of "cup" rockers, that go straight under the camshaft and straight over the valves. I'll see what the mileage is with woodtick's advices, of still sucks, I may have to buy a set of rockers. Btw, how much is that, if memory serves me right should be about $800, correct?

Edit: I'll pay attention at cold start, usually bad hydro rockers make a bad tick till oil reaches to them, at least that's what I know. Anyways, if nothing works, I guess I might have to try changing them, lol.
Author:  kjjet [ Sun Jan 27, 2013 10:23 pm ]
Post subject:  Re: Mileage question
The Hyd lifter and rockers come in a set. Total of 16. People have been getting them imported for less $$$ not sure how much. Its a labor thats bad.

Hope its not.
Author:  thermorex [ Mon Jan 28, 2013 11:26 am ]
Post subject:  Re: Mileage question
I certainly hope it's not that. But I will look around and buy the parts for now, just in case. Eventually, they will need to be changed at some point since I plan on keeping this jeep.

Quick question: is this (worn rockers) such a common problem for this engine? Looks to be a bad design. I always have enough oil and i replace it always in between 5-6k miles... Other than being a gasser, I love my xj engine, lol, it's almost unbreakable.
Author:  kjjet [ Mon Jan 28, 2013 12:35 pm ]
Post subject:  Re: Mileage question
Rockers have been a problem with engines normaly over 100k due to the EGR soot being induced into the engine. (at least thats what i think) Do you have a GDE tune? The longer you have one the better for your engine. Changing the oil at 5k will also help.
Author:  thermorex [ Mon Jan 28, 2013 5:09 pm ]
Post subject:  Re: Mileage question
I don't have a gde tune yet, but planning to get one. I had been driving the car with maf unplugged for about 30k miles (I have now 120ish). I know that orm doesn't do what gde tune does, but is definitely better than without. I had a chip (det - diesel Eco tune is the name), got it before knowing about gde and I stopped using it about 15k ago due to the fact it put my car on limp mode after a while, probably bc it increases the rail pressure. That makes me wonder if the sensor on the rail didn't go bad, even though I have no odb code other than the maf unplugged.

Regarding oil change, I drive about 75% hwy and most distances are over 500 miles. I have the xj for driving around the house/offroad due to the fact I can find parts everywhere. That's why I go around 6-7k miles with an oil change on crd.
Author:  TennesseeCRD [ Tue Jan 29, 2013 9:06 pm ]
Post subject:  Re: Mileage question
Been getting poor mileage with mine as well I haven't checked the rockers yet but all roads lead that way because I've looked into everything else. I'm getting 17mpg everyday driving and the best I can do is 23 on a road trip. I didn't find out about the rocker problems till reciently but I'd bet that is the problem with your's as well. Good luck.
Author:  thermorex [ Wed Jan 30, 2013 8:54 am ]
Post subject:  Mileage question
Do yo have any funny sounds that may be caused by rockers, or you think it's that by elimination process? In my case there is no weird noise, engine sound seems to be the same as when I had 27 mpg on hwy. I know they are hydro, and oil may take away the noise, but even at cold start, there is no suspicious sound at all. btw, is there any way to see if the rockers went bad, other than taking the camshaft cover off and looking/checking them?

Thanks everybody for help!
Author:  kjjet [ Wed Jan 30, 2013 9:33 am ]
Post subject:  Re: Mileage question
thermorex wrote:
Do yo have any funny sounds that may be caused by rockers, or you think it's that by elimination process? In my case there is no weird noise, engine sound seems to be the same as when I had 27 mpg on hwy. I know they are hydro, and oil may take away the noise, but even at cold start, there is no suspicious sound at all. btw, is there any way to see if the rockers went bad, other than taking the camshaft cover off and looking/checking them?

Thanks everybody for help!


1. Whats the miles on your CRD?
2. I had no warning noise or starting issues.
3. The EGR is puting damanging exhaust thru the engine. A GDE tune is helpfull?
4. No there in no way of knowing how your Rockers are unless the intake is removed.

I would say if you never had it off prior to your 2nd timing belt change I would do it with the 2nd belt change.
Author:  thermorex [ Wed Jan 30, 2013 9:48 am ]
Post subject:  Re: Mileage question
I have a little over 120k. I had timing belt done at little under 100k, but didnt change the water pump bc of lazyness... it seemed in very good shape so I didn't change it. Now I regret since I always think it may fail, lol. What sucks is that now the crd is in Alabama (I live in Cleveland OH), where I am with work and obviously I have no tools to do the job myself here... May need to pay a mechanic to inspect them, and if I do that I may as well replace them if they are prone to go bad...

I just ordered a GDE Eco full torque yesterday btw. I didn't know they have a flash tool, thought I need to go in Michigan for it and couldn't find a good time. Wish I knew that earlier...
Author:  kjjet [ Wed Jan 30, 2013 1:27 pm ]
Post subject:  Re: Mileage question
As far as the water pump. They last a long time and will start to leak prior to failure so. That's no problem. I plan on changing mine at the 2nd belt change.

GDE tune. Good! I removed my computer and sent it to GDE and Keith sent it back the same day he got it. 3 to 4 days total.

Sorry to here you live in Cleveland. I worked there for 8 long years. Not good

Inspecting the Rockers is a big job and yes replace all while you have it opened up.
Author:  thermorex [ Wed Jan 30, 2013 8:35 pm ]
Post subject:  Mileage question
That's what I thought with water pump also, just heard of some cases when bearing gets stuck on them, but I find it unlikely since its cooled by the engine coolant and its likely to leak prior to seize. I plan to stock up some parts, because if I'll do the rockers, I may as well doing a new timing belt w all pulleys and water pump then. I'll see what mileage I get with gde tune and warmer weather here in Alabama first.

And yea, lol, Cleveland weather sucks big time, it's not that cold but it's always cloudy in the winter.

Would you happen to know the part numbers for rockers and lifters? I looked at parts.com but didn't find them, maybe I need glasses, all I saw was everything but them on the cylinder head parts...
Author:  thermorex [ Thu Jan 31, 2013 12:25 pm ]
Post subject:  Mileage question
Never mind, got that from id parts. For whoever is interested, parts.com has a cheaper price for the oem rockers (with about 10 bucks/rocker). Part number for rocker is 5066780AB. (Edit: I fixed the part number so now it is the correct one)
Author:  TennesseeCRD [ Thu Jan 31, 2013 6:57 pm ]
Post subject:  Re: Mileage question
thermorex wrote:
Never mind, got that from id parts. For whoever is interested, parts.com has a cheaper price for the oem rockers (with about 10 bucks/rocker). Part number for rocker is 506678AB.

I got this at parts.com: "Part number 506678AB was not found".
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