MAP sensor

I have an 88 XJ Laredo. I runs but is really rough. It is running real rich at the exhaust. If I unplug and cap the vaccuum line at the MAP sensor and cap the line it runs better, but still really rich. Does the MAP sensor need replaced?:flame:

Check the vacuum hose connections at the TB and MAP sensor, and the condition of the hose itself, repair/replace as necessary.

Test the MAP output voltage at the sensor connector pin "B" ignition ON and engine OFF with ground pin "A". You are looking for 0.5 to 1.5 volts.

Should have same voltage as above at ECU pin C-6 (for the 1990).

MAP supply voltage, pin "C" should be 5 +/- 0.5 volts, with same voltage at pin C-14 ECU.

Other contributers to rich conditon: engine not reachings 195 degrees, coolant temperature sensor bad, O2 sensor bad, exhaust leaks causing O2 sensor to read lean.

Thanks for the info as to where to begin looking. Where would the exhaust leak have to be to cause the O2 sensor to read lean? Would a leak just after the catalytic converter cause it to read lean? Or would the leak have to be prior to the converter, closer to the manifold and the sensor?

Leaks before the o2 sensor can make it read lean, anything downstream shouldn't have much, if any, effect on the sensor.