My 4.0 starts up fine and then goes into a rough idle. I have cleaned the original TPS sensor and swapped it with another used one. The other thing that is connected to the throttle body i have also swapped with another used one(the one where the little square fits into the grooved plastic Im assuming its hooked to the butterfly). I could not find a map sensor to swap out but tried cleaning inside that, could that be the problem? I go thorugh ridiculous amounts of gas when the check engine light finally does come on, but then i just pull the negative battery cable, reset the computer and it runs with no engine light for a while. Everything got submerged in water. I have checked connections and cleaned them out and vacuum lines. A computer hooked up to it said Fuel system lean at bank 1, and the turn key method I believe came up with a 25 code. Please give me all possible ideas because I am running out of them and gettin ready to get rid of this thing if I can't trouble shoot it, I've spent weeks!
also on the firewall to the right of the valve cover theres a little black computer sensor(brain freeze cant think of what its called) but has ony 1 plug going in..make sure thats connected and tight..i had that problem before and that fixed it..if i find a pic of an enine bay ill mark it out for you
big lift, sick tires, awsome accessories, alot of custom work.
not my engine but this is what i was talking about
That's the MAP (Manifold Absolute Pressure) SENSOR. It senses intake manifold vacuum, and the ECU uses that, along with other inputs, to calculate F/A ratio, and adjust fuel injector pulse duration.
I don't own an XJ any longer, but I still think they are the best of all the Jeep products ever made. My XJ was my favorite vehicle in my 50+ years of driving.
So...I stick around and give advice.