How to replace MAP SENSOR Jag x350 j8 2004.

 

If I'm understanding what you're looking for, you need to replace the sensor on the back if the intake manifold, that you can't even touch.

You have to remove the manifold. I removed mine on my '07 XJ8 to replace the coolant hose in the valley of the Vee. There are a lot of electrical connectors and a couple of vacuum connectors (at least one of which probably feeds a broken plastic pipe which will need to be replaced,) and then tow connectors on the back. One of those two you can touch but not reach well enough to disconnect (the fuel temperature sensor at the back of the right-hand fuel rail) and the other you can hardly even see, much less touch (the MAP sensor.) you also have to remove the EGR hoses and the coolant lines at the throttle body, including the one that disappears under the manifold into the Vee. You should be able to disconnect the brake booster pipe, as it has a disconnect just above the back of the manifold.

With everything disconnected except those two electrical connectors, you need to unbolt the manifold and move it forward to the extent of the wires still connected, but you can now reach those and disconnect them, and remove the manifold from the car. The MAP sensor is right there on the back.

When you get new gaskets, make sure you get the metal ones with the tabs that bend up to hold the gaskets on place against the manifold ports. The cheap cardboard gaskets are all but impossible to keep lined up when reinstalling the manifold. Connect the two hard-to-reach connectors before actually setting the manifold back in place.

If, like me, you repair broken vacuum lines, especially the one that goes to the fuel pressure sensor at the front of the right-side fuel rail, you'll get some check-engine lights for a few days, because the fuel pressure sensor will read differently with proper vacuum being applied to it than it has been reading for however long the vacuum hose was broken, and the pressure sensor and the O2 sensors will be fighting each other over the mixture for a while. The codes will be system too lean bank 1 and system too lean bank 2. Implying a vacuum leak, which would be odd because you just fixed a vacuum leak. The actual cause is that the fuel pressure sensor now reads higher fuel pressure than it has in the past, and when comparing the pressure to the airflow reading, it reduces fuel feed, which makes the O2 sensor throw a lean code. It will eventually self-correct, so just keep clearing the codes when they appear; it's all right. Once the ECU learns what's going on, and the mixture adjustment zeroes in on what's actually happening between airflow and fuel pressure, it will stop throwing those codes. I had them when I first repaired that line, wasted a LOT of time troubleshooting, but the codes got further and further apart and eventually stopped. When I though about what the fuel pressure sensor does, and the fact that it now has vacuum when it didn't before, I figured out why it was leaning out the mixture. Like i said, once it zeroes in and all the sensors (air flow, fuel pressure, and exhaust oxygen) agree on what's actually happening, it's fine.

 

MBOLO, as I am replacing all of the hoses on my 04, I discovered that I need to replace the Map Sensor too. I still haven't been able to disconnect it from the plug. I have sprayed it with lubricant & will continue to make inquiries and play with it until it succombs. A lot on this car is like a woman! Good luck, Steve S.

P.S. I can ditto everything WFooshee said above.

 

THAT... was *super* helpful!!!

Thank you!

 

You can zero the fuel trims (which the above means) by disconnecting the battery (a "hard reset").

 

Most of us do, even if only by "accident" AKA, normal part of a repair procedure.

But it was useful to have some insight as to what CAN be going-on, 'incrementally'. too.

 

I did not realize the hard reset would remove the PCM's learned maps. I've done the reset several times when I had a weak battery and just didn't drive the car often enough to need it 100%. I'd do the reset, jump it off, and off I'd go, then park it for another week or two and need the reset again because things wouldn't work.

 

I keep mine on a decent "maintainer" charger, but.. now and then rob the AC power cord off it for an air-compressor, corded power tool, pressure-washer, or to charge the Rover.... and forget to reconnect the XJ!

MOST of the time, it has kept the modules sweet, even if it hasn't the juice to start.
MOST of the time, I just attach the/a "faster" charger and go off and do other things for several hours.

"Hard" resets have been really rare. No more than one in every two or three years?

But the more we share, the more "gotcha" teeth marks on the ****-tissue we can have a better chance to avoid.

 

Started using a maintainer here, too. The Jag is not my daily, and if it sits for a week, I get stuff like "Cannot apply parkbrake" and "Cruise unavailable." I purposely park at home with the parkbrake not set (push the button down when removing the key) because "cannot release parkbrake" is MUCH more difficult to get out of!

If I forget and it gets this way, I do have to reset the parkbrake with a battery disconnect and touch the cables together, then either jump it and drive, or leave the maintainer it on it for a while. Simple charge will not reset the parkbrake once it does a "Cannot."