So we’re having some issues with our 1990 XJ Limited w/ 4.0 non-High Output, Automatic.
At starting, it’s revving between 1,500 – 2,000 (600 is normal for us as of yet)
When shifted into Park, the RPM’s rev very high (well above 2,000), as well as makes a loud “ka-thud” sound when shift into Park or Reverse.
When driving, it shifts with a clunk and a soft jolt (this was happening mainly shifting into Drive)
RPM’s seem to be in the normal zone when driving at freeway speeds.
Idle is raising “by itself”, carrying the Jeep down the road at a speed upwards of 20 mph without touching the accelerator. When this was happening, it was also very hard to brake, really had to push down on it hard, and it crawled to a stop, very slowly. Release the brake, and the Jeep goes forward still at much greater force than normal idle, as if idle is sticking.
When we just parked it, the idle was upwards of 3,000 RPM, in Park.
Hoping someone out there has some input to this dilemma , we don’t wanna blow our engine or get into an accident. Help please if you can!

Thanks a bunch! -Dave

 

check for broken or disconnected vacuum lines under hood .

 

Thank you!

 

check the hose hooked to the brake booster also