I have a 1993 4.0 xjs and I've been trying to fix a bad cold start and bad idle problem for several days and replaced several sensors that the computer said were bad, but the idle improved somewhat but is sitll not correct. I decided to remove the throttle body and completely clean it. When I removed the T.B., I found 2 small pipes inside the intake,(one larger then the other), coming up just behind the throttle body inside the intake manifold, there also is a wire and sensor coming into the some area. Both pipes were completely covered with carbon, enough that I don't believe air was even getting in. I had to use a small screw driver to scrap the carbon away. My question is what do these small pipes do and what is the sensor under thems purpose. I hope cleaning all this carbon away helps the idle.
I also completely cleaned the T.B., but did not remove the T.P.S, but did not put any power to it, so I'm hoping that I didn't cause any damage to the T.P.S.. I will find out in several days, cause I am going to let everything dry before I reinstall the T.B. and start the car.
Any information on what the purpose of those pipes and the sensor is, would be greatly appreciated.

 

Hello, I have a 96 XJS 2+2 that had me thrown for a loop regarding the bad idle. I used a different code reader and found that part of the problem was the Mass Air Flow Meter. The mechanic had cleaned the Throttle Body and changed several parts. The idle issue continued. I purchased a used MAFM from a wreaking yard for $100 and replaced the original. The car is running a whole lot better. You might check that MAFM to see if it's not functioning.