Continuing my adventure with my 96' XJR.

So I just replaced my two exhaust manifolds... which eliminated my previous problem of the car stalling.

However, now two other things happen:

1. When in Park or Neutral car revvs up really high and then drops the revs suddently. Then repeats.
2. When I am in Drive gear, and I break - the car keeps pulling forward (no matter how hard I press the break, I can't completely stop). Once I shift to Neutral - breaks engage and car stops immediately.

Has anyone ever seen symptoms like these?

 

first, check for codes with your scanner.
second, clean throttle body.
third, check tps and iac.
lastly, check for air leaks before the throttle body and or at the tb adapter, there are three vacuum hoses at the point. Now that I think about it, the same symptoms happened to me and in my case it was one of the vacuum lines at the throttle body adapter that was disconnected that caused the erratic idle.