longtravel1

I bought a 89 XJ yesterday. The previous owner said that the MAPsensor was not working properly and had the vaccuum line unplugged. This made it very hard to start and very tricky on the throttle. i went to get gas and it has died. I am new to Jeeps so can anyone help me trouble shoot? What does the Map sensor do? Could it be computer prob??

93XJLI

...just get a new MAP sensor then.. it regulates air and fuel flow

BuckB91XJ

Your MAP sensor is your Manifold Absolute Pressure sensor. What this sensor does is monitor manifold pressure and based upon it's input the computer adjusts fuel and spark to keep the Jeep running right. If the MAP sensor fails or is unplugged, it throws off the whole loop sysem of the computer. It will cause the Jeep to run really bad and lack power, fuel economy will get very poor and in some cases the Jeep will stall.

longtravel1

Thank you. I am in Tucson. Any Idea who would have one? Pep Boys or Auto Zone or would this probably have to be ordered?

BuckB91XJ

Any auto parts store should have your MAP sensor. Only go to the dealer if you can't get it anywhere else. They will charge the most for it.

longtravel1

Buck,
I bought a new MAP sensor but it is doing the same thing. It will start right up then run perfect for about 5 seconds. Then it dies. When I unplug the vaccuum it starts rough but will idle. Is there something wrong in the throttle body? Any Ideas?

BuckB91XJ

Well, vacuum and vacuum leaks are crazy to troubleshoot sometimes. On my 91 with the 4.0 HO motor, the vacuum line for the MAP sensor comes right out of the intake manifold. Now, the vacuum line for my son's 87 Renix 4.0, comes out of a grommit in the side of the Throttle Body. Closely inspect that whole line for small cracks and that goofy grommit for a possible vacuum leak. We ended up grabbing that whole vacuum line, grommit and all, out of a donor XJ in the JY when my son's developed leaks.