2T2-crash

My Jeep: 87 XJ, 4.0. The engine has had a cooling system swap out with a 90's model open cooling system to include radiator, t-stat housing and heater control module (spitballing the term... The plastic piece that connects the water lines to the heater).

The cherokee keeps about 185-190 now, iirc 210 is normal operating temperatures and that anything less puts the XJ in warmup-mode... Pumping fuel into the engine at a higher rate.

How can I get my temps to raise? Or.. How can I get the jeep to think the temps are Hightower? Would doing so be bad for the engine?

How can I increase my gas mileage? I get about 140 highway miles to the tank or so. (I still need to install a new speedo gear since installing 245 tires

Radi

185-190 is perfectly acceptable. IIRC 160 is the tipping point. What general condition are the ignition and fuel systems in?

2T2-crash

The plugs and wires were replaced along with fuel filter, sending unit and a fuel system cleaning by Sears auto. The jeep sat for seven years while I was overseas but I remember the mileage sucking pretty bad after the swap out back the . Would swapping from stock tires to 30" without a speedo gear change cause that drastic of a perceived loss?

spaz_22

first you need to list what mods you have done. suspension wise, tires, gears, bumpers, engine wise. how many miles are on the motor, and what mileage are you getting now. What mileage do you expect out of it

Radi

Well, your speedometer and odometer will be 4.2% low with 245's. If you are using that to calculate mileage you'll come up lower than what it really is.

7ate9

90xj and mine runs half way 210 I think but then the second fan switches on and it starts to cool

7ate9

My 90xj runs around 180 sometimes half way mark 210

2T2-crash

Suspension and axle info is right next to my name by clicking the 1987 cherokee (not being snarky here).
Stock bumpers, stock engine aside from the cooling upgrade.
It's a boneyard lift running 245/75/r16s on stock D30/D44. The engine has what I estimate to be about 50,000 miles on the block for sure, not positive about the rest (my uncle blew the engine and replaced it a couple years before I bought it from him).

I'm estimating about 10 mpg out of my jeep if sticking to the highway, I would figure for a bit better.

2T2-crash

My secondary is wired to a guarded switch on the dash, I only hit 210 degrees during serious wheeling. Which has only happened twice.

Radi

That is low. I'd expect 18-20 highway easily even with the larger tires with an '87. The HO's seem one or two MPG worse for some reason.
Do you smell gas or have any indication it's running too rich? What do the plugs look like? Blockage in the exhaust? Is the trans shifting to OD and the TCC locking up?

2T2-crash

I'm getting about 140 to the tank, I believe it's a 14 gallon tank.
I'll check the exhaust in the morning.
The transmission shifts fine, it's only ramped up on startup a couple of times but I believe that is a TPS issue.
There should be no exhaust blockage, it has a newer muffler and a hollow catalytic converter that needs to be replaced with a good one (young and dumb).
I'll check the plugs but I've only had it out of storage for a month.