This afternoon and one time last week my otherwise fine running XK8 (MY2000, 95,000 miles) is experiencing a high idle when warm- it holds at about 1,200 RPM. It happened today after a 150 mile expressway run while cruising through town toward home.

It started surging a bit at about 40 mph. I could hear what I think is the VVT clicking madly - several times per second - while I'm cruising at 40-45. I received a Failsafe warning as I pulled into the drive.

I pulled code P0507 -"Idle Control System - RPM Higher than expected". This is the generic OBD definition, does someone know the Jaguar-specific definition and it's diagnostic links?

I cleared the code and all has returned to normal for now.

The rapid clicking of the VVT is a clue to somethng, I'm just not sure what.

My throttle body was rebuilt about 25,000 miles ago and is spotless and the electrical connections are 100%.

Thanks!

 

The JTIS description for that code is, as you say, idle rpm higher than expected. Their explanation for it is:

Throttle assembly failure

No mention of VVT on this one. Maybe the ticking is something loose and flapping in the inlet trunking?

 

I'll give the small parts of the inake the once over and look for split connections, etc. I just went over the accordian hose and the throttle body gasket recently and they're good.

I'm pretty positive I was hearing the VVT solenoid actuating. I wasn't thinking and cleared the code - and the problem - before I had a chance to stand next to the thing and listen. It will return I'm sure and I'll get a chance again.

P0507 is a pretty generic and lame code. It certainly can be, and is most often, triggered by intake air leaks but I'm betting that something else is fooling the throttle body/VVT system into thinking the engine should be making more power than it needs to at that moment.

Thanks for the fast response, I was trying to locate my CD drive and JTIS disc and get it to work with this new computer...

 

The VVT accurate around 1300 rpm, so you may well here them going in and out as the revs go up and down but not normally rapidly.

I would do as you are and give everything a good clean, spray some WD40 around joins and known problem areas looking for air leaks, you will know if the revs pick up

 

I did a search for P0507 today (3/9/14) to help deal with a current issue and my old post came up!

I should have tidied this old one up by noting that the fault was a loose throttle body electrical connection. It felt seated and snug but the retaining tang was broken off and it would eventually work itself out of the connector and cause weird problems doing so.

I devised a set screw arrangement to hold it all together. That worked for a couple of years and when the trouble returned I recently added a Zip-Tie to help hold the wire loom more tightly.

The P0507 code has reappeared this spring, on and off. I'm back to looking for air leaks...