93 4.0 running cold?

the jeep is a 93 yj with the HO 4.0L.
when I bought it I thought the stock temp guage was not working properly, it barely registered just over 100*. so I picked up a new stock temp thermostat, and a mechanical temp guage. well, even with the new T-stat, and the sensor for the new temp guage mounted in the upper radiator hose(just past the water neck, as close to the stock temp sensor as posible), I'm still not getting any temps over 135*. I could be wrong, but I think this low temp isue is causing the computer "think" the engine is'nt warming up, and is keeping the air/fuel mix on the rich side(exhaust smells rich).

dose anyone have any ideas of what I should check next to try to resolve this low temp isue? I've already tried blocking off the grill, and that made no difference in the temp readings.

also, is there any way to "trick" the computer, to make it "think" the engine is warm? and if so, would doing so cause the computer to lean the mixture any?

well i'm not sure why but apparently the thermostat is just opening to soon and causing your jeep to stay cool but i've seen things to "trick" your computer like piggy back devices and other things like that. they attach to the air flow sensor but i'm not even sure if they make them for jeeps check ebay or a 4wd site

well, the thermostat, as well as the stock temp sensor are both only a couple months old. also, I've tried blocking off the air flow through the radiator, and still couldn't get any temp readings over the 130-135 degree range. and the sensor for the mechanical guage is in the upper radiator hose, as close as posible to the water neck and stock temp guage.

I did just find a resistance chart, and wiring diagram for the temp sensor and computer, so I'm going to check out all of that just to make sure that it's working properly, and maybe pick up one of those radiator caps with a built in temp guage, and see what happens.