Yes, they do go bad. They also can appear bad becuse the wires aren't plugged in well or the connection is dirty. More commonly, the vacuum line going to them is leaking vacuum, sendig the MAP a false signal. I believe they were the same from 87 to at least 95. Your local parts guy will know. The MAP sensor reads your manifold vacuum and sends a signal to the ECU so it can adjust fuel delivery according to engine load. If it's bad, your Jeep will run very rich, blowing black smoke.
how about a popping in the intake ? new fuel pump ,filter ,dist, plugs, wires, cap rotor, cleaned the throttle bodie, seems to happen while the jeep is just about normal temp i have replaced all of the above i am getting some carbon on my hand if someone revs it up and i stick my hand behind the exust , not much though , like i said its while it is warming up or about 4 miles from home , work while driving , cel doesnt go on though
Are you saying it does this only while warming up and it's okay after that? I would look for vacuum leaks in all those vacuum harnesses under the hood. The rubber connectors can deteriorate and the hard plastic lines can crack or develop pinholes. Your CCV system, the lines to the valve cover, should be removed and cleaned to be sure they aren't clogged. About $8 to replace the rear tube with grommet and orifice. Did you check out yur MAP vac harness and connector yet? I'd quit throwing expensive parts at this and look for maintenance items like these that need to be addressed. You ought to refresh all you grounds at the dipstick tube and head to firewall while you're at it. Refresh means removing, scraping, polishing and reinstalling. Clean and shiny.Check all your intake manifold bolts/nuts and see if they have loosened up, too.
Map sensor and coolant sensor can be tested with a manual and a meter. Both are involved with determining fuel/air ratio.
Have you verified fuel pressure at the fuel rail? Would be one of the first things I would do if it were mine. Gotta use a gauge. Backfiring in the intake can be indicative of a "lean" condition. You replaced the fuel pump but there is still a regulator at play here.....Compare your readings to factory spec.
Test your way to a solution.
99 Cherokee, 4.0 AW4, NP242
Past Jeeps: 49 Willys, 81 Scrambler, 88 Comanche Without "data", all you have is an opinion!
changed temp sensor ok well i changed the one in the termostat housing is that the correct one ? only happens if its colder out and i get in and drive , if i shut it down and restart no problems for the rest of the day ,, again i did change the sensor in the termost housing not the back one with one should i have changed ? any other suggestions