2003 4.2 s rpm flucuates at moderate speed
 

Hi

I have a 2003 4.2 S. I've just noticed that the engine pulsates at moderate speed around 45. You can hear the rpms surging up and down and see it on the tach. It goes away after warm up and/or at high speeds. Car runs smoothly otherwise. I can't tell if it's a transmission issue or something else.

any ideas?

Kent

Kent welcome to the forum.

First you should really go to the "new member" section and introduce yourself per forum protocol.

Second for future use PLEASE add your vehicle details in your signature by using "User CP" in upper left corner on any page of this site.

I have moved this thread to the S Type section for better exposer.

Sounds like you need to get the TCM reconfigured to newer software. TSB S-307-14 describes the fault and the cure.

"Summary
S307-14: This Technical Bulletin has been issued to address a customer concern of a surge in
excess of 150rpm during engine warm up, at a temperature of 30°C to 50°C and at a vehicle speed
in the region of 40mph (64.3kph) to 60mph (96.5kph)."

bob gauff

Agree with motorcarman,:icon_imnotworthy: common issue.

https://www.jaguarforums.com/forum/s...-needed-68933/