One suggestion in the JTIS to address the high idle condition in my 2000 XK8 is to inspect the Cruise Control Vacuum system for leaks.

Can anyone provide a diagram of this piece of plumbing?

Thanks!

 

The AJ27 Engine in your car does not use a Vacuum Cruise Control System.

The ECM controls Cruise Speed directly via Throttle position.

However, a Vacuum Leak could indeed affect Engine Speed.

 

I've been experiencing a P0507 High Idle code recently. My 2000 XK8 ran beautifully all day today and went into failsafe mode just as I arrived in the garage at home...pulled the P0507 code.

I went over the probable leak areas AGAIN and found nothing. I decided to do a hard reset just to see what might happen.

Oh boy - on the restart it ran to 2,500 RPM, then began to cycle between 1,200 and 1,600 in a regular, even pattern. I tried several restarts and the same thing happens each time. It will eventually set the P0507 code and go into Failsafe mode.

My TB was rebuilt a couple of years ago by ASI. I recall that there is a procedure for helping the throttle body get situated after a hard reset. Can anyone help me remember what that is?

Any other ideas?

Thanks!

 

The issue is a cracked cap on the TPS. ASI did the rebuild and knew immediately where to look. Apparently, they cut the cap open as part of the rebuild and epoxy it back on. It's a spring loaded device and the pressure against the cap combined with heat and vibration causes it to let go.

It's a routine problem for their older rebuilds and is covered under the warranty.

If you've had a rebuild you might want to check into the condition.