New Owner: 1997 XK8 coupe - cruise control craziness

[Wolvesboy]

Hi All, apologies for the long post. Here goes,

Just picked up this car. Runs well with 100k on clock. It had an intermittent ABS issue that I thought I would look into later.

However, whilst driving in town I went to use cruise control (centre switch) and the car goes nuts - revs go up & lowest 1200 even at standstill; gearbox fault warning; shifts become harsher; engine light comes on and then stalls when coming to a stop. Does not start for 3/4 attempts.

Turned off cruise on the centre switch & car turns on and drives pretty normally! I had to do120 miles on the M1 and the gearbox was not perfect/ as smooth as it should be. Turned off into town and car goes into Iimp mode (revs but goes nowhere). Turned off and on and seemingly cleared the issue. Got home.

Next day, checked resistance at each speed sensor and the continuity of the wires and all good. Torque lite OBD2 reader gives P1245 & C1175 codes. Drove today and mistakenly pressed the cruise switch on - same issues as before (high revs, warnings etc) but stalls immediately upon stop. Turn on and moving into gear is a massive thud. Go home. Turn off cruise and car. Restart 2 minutes later and the car performs faultlessly all afternoon for 60 miles driving!!!

So....... I am confused here - speed sensor, brake switch, crankshaft sensor?? But everything is good until cruise is switched on!!! What to do next? Any help is much appreciated.

Thanks.

[O.T.H]

Deferentially the 1st thing is to check is the Battery  the  Jaguar's rely on a good battery --how old --if over 5 yrs

old its on way out - or could be alternator not charging ????----------could be when switching cruise on takes

too much power ??? ---Just a thought ???

[Wolvesboy]

Thanks for the reply,  Frank. The car runs like a dream otherwise!

Battery engine off is 12.35v. I will try it with engine running and under Air Con load to see if this causes any issues. 

[Jimbov8]

On 7/4/2023 at 10:20 AM, Wolvesboy said:

Thanks for the reply,  Frank. The car runs like a dream otherwise!

Battery engine off is 12.35v. I will try it with engine running and under Air Con load to see if this causes any issues. 

Far too low, should be 12.8v for a fully charged battery. Try giving the battery a charge and see what happens.