Steffen84

Hallo everybody.

My name is steffen and I am from germany. I have a 1990 cherokee 4.0.
what i have done since I bought it:

paint black
new brakes all the way
ZJ springs and spacer, add a leaf and shackle (maybe 3" lift)
8x15 with 31x10.5 MTs
new rotor, cap, cables and spark plugs

I noticed that the temperature via the gauge sticks at half way to the middle position! Not more
Idle is at 400rpm in neutral and d with brakes

What can cause this bad milage?

djb383

The extra weight of the lift components and heavier tires, the taller tire diameter, possible brake dragging and driving conditions (style) can/will have a negative effect on mpg.

Steffen84

welded the manifold because of cracks, fogot to tell you that.
This is not all that causes this bad milage but I hoped so.
I have read a lot drivin 17mpg and more with the same setup. I think there are other causes...

I drive like a grandpa no more than 2000 rpm and no full even less than half throttle acceleration...

drhoward1988

Gears would be your next step. You've changed the ratio by adding larger tires. I'd recommend 4.10s if you plan on staying at 31" tires.

twinkiedooter

My 94 ZJ got about the same mileage when I drove around town a lot (11 or 12MPG). If I went 20 miles one way to work I'd get around 18MPG. I did have bigger snow tires on her. 225/75R/15 Goodyear Wrangler Radials. Good tires if you can get ahold of them over there. Tread lasts forever!! I did notice after a complete brake job I did get better mileage. The calipers were frozen on the front axle. So look over the braking system very carefully for this. Also emergency brake on can make a huge difference. Happened to me and had to have corrected. I keep meticulous gas records on my vehicle and when MPG goes down I start looking for the culprit. Pays to pay attention to the MPG.

Having such an old Jeep you will have a hard time getting body parts for her. Now over here the older Jeeps are being taken out of the junkyards. Even the 97's are hard to find up here in Ohio.

I am a little old lady and have driven like one for many years which really saved my 94 that I had for 12 years and had to junk recently due to frame breaking due to rust. Rust is the only thing that can successfully kill a Jeep. Keep that in mind. You did say you did brake job though but relook at calipers. Also the operating temp should be just a hair below the 210 mark on the guage. You may need to change out your thermostat as it sounds like you may have one of those 180 degree units. I replaced mine with a 195 OEM unit. Now my girl runs just a hair under the 210 hash mark on guage.

My girl is all black also....even the grill.

Steffen84

I welded a lot but looks good now :-)

What about bad sensors because of age? ( O2 temp and so on) have read a lot about issues with them? Would it be good to check them, toi?

Where can I get such a t-stat? Any link?

My Boy got 233000km on the clock and I do not think someone changed something before I bought it. What about that seafoam?

Thanks a lot !!!! :-)

twinkiedooter

Just remembered something about my 94. She would ONLY get great gas mileage if I used HIGH TEST. If I tried 87 octane she would get horrible mileage. You may just have a prima donna like my 94 and demand higher octane to get good mileage. I figured what do I want high gas mileage or save a few cents? At the time gas was $4 a gallon for high test so I just bit the bullet and bought it.

Steffen84

We got not less than 95octane here in germany ��

Here is my toy

kgm

US and EU octane ratings are different. 87 is the US 'low' grade typically.

twinkiedooter

I like your toy. Love the woods/trees also. I'm jealous....wish we had the 95 over here. Your tires say it all. They are probably VERY heavy and will bog down your MPG.

You also need a hood/rock guard to keep crap off your windshield and keep flying rocks from smashing out the windshield. They are plastic and cost less than $50 on Ebay. I also have the 4 window/rain vents so I can open windows in summer when it rains and have some air. My A/C blew up long ago. Got mine off Ebay also. I think they ship to Europe. Worth the cost and kinda dresses up the girl a bit I think.

mschi772

I didn't see anyone mention this, and it's quite important.

You have 31" tires but said nothing about changing your speedometer gear to compensate, nor did you mention compensating for the increased tire diameter mathematically when calculating MPG.

With 31's, you're traveling 10% farther/faster than your odometer/speedometer are telling you.

Changing your speedo gear is very easy -- http://go.jeep-xj.info/HowtoSpeedoGears.htm

All of the other posts are useful, too--especially regarding the need to regear your axles. I could list a thousand things, but MPG concerns and methods of improvement have been covered so many times that I can't bring myself to write it all again.

Blown03SVT

Noticed you said you are idling at 400rpm in neutral, you should be at about 700. Have you tried cleaning the throttle body. Also, what plugs are you running? The 4.0 doesn't like the fancy plugs, cheap coppers works the best.

Steffen84

not cleaned it yet.

I used some bosch plugs but installed them yesterday. so I can not tell you wether they are better or not, but the old ones looked realy old

will post a pic later.

I need such an 195 t-stat for my renix (with that little hole) where can I get this?
I suppose she is not warm enough an the temp sensor tells the ecu to put some extra gasoline in...!?!

67 GMC

This will make some difference on the calculation of the mileage. Also, are you calculating the mileage by filling the tank, driving for some number of KM, then going back to the gas station and refueling to the same point and recording the volume of fuel used? That is the best way to do it. Also, are you converting the litres used to US gallons (not British imperial gallons)? 1 US gallon = 3.78 L, 1 Imperial Gallon=4.545L. In Canada, where we have the metric system, the car dealers love to post MPG figures using Imperial gallons to make it look like the cars get better mileage than the accepted method using US gallons done in United States. For example, if your Jeep got 17 MPG in the US, a dealer in Canada would say it was getting 20 MPG and not be incorrect (but misleading).


Octane numbers are the average of RON and MON in North America ((RON+MON)/2). Most of Europe uses RON only. So Shell V-Power 98 in Europe would be 94 Octane here. What US and Canada call "Regular Unleaded" is 87 Octane but in Europe it would probably be 91 Octane. Similarly, "Premium" unleaded is typically 92 Octane here but would be 97 Octane using RON only.


Here's a good site that calculates the difference in tire size as well.


http://tire-size-conversion.com/tire-size-comparison/

cruiser54

52028186 thermostat from the dealer.

Click on the "pink link" in my signature below and do Tips 1,3,4, and 5.

Make sure your odometer reads correctly.

I would replace the O2 sensor with an NTK brand and clean your throttle body. Tip 11.