Small rpm surges all speeds

Need to take to a shop with a GM tech 2 or higher scan tool. These tools can actually display various sensor readings and voltages in real time and can be used while driving the car to recreate the issue. These are super expensive scan tools so most shops don't have them. Call around or bite the bullet and have a dealer do it. The money you spend on a correct diagnosis will be saved by not throwing random parts at it based on guess work.

Thread: 6.0 V12 XJS High RPM When Warm - Jaguar Forum.co.uk

www.jaguarforum.com/showthread.php?t=54266
Mar 3, 2013 - I recently bought a 1993 6.0 V12 XJS and when it is started from cold it runs ... to 1300 RPM so it wants to surge forward when braking which is strange. ...Classics · XJS 3.6,4.0,5.3 & 6.0; 6.0 V12 XJS High RPM When Warm ... You might want to adjust the aux (extra) air valve to bring the idle speed down.

Idle air control motor. Clean it or replace it.

When you say " surges in rpm" you mean it surges when you give it gas, press down on the accelerator. It could any one of a dozen reasons for this; dirty air filter, dirty gas filter, foiled spark plugs, ignition problems, faulty fuel regulator faulty speed sensor, etc. Have the car's computer scanned for trouble codes which will identify where the problem is. Auto Zone and Advance Auto will do a scan.

I had the same problem with my 2005 Cobalt LT. I fixed it by removing the throttle body and cleaning it. There was a lot of build up in there causing the the valve to stick.

Replace TPS (throttle positioning sensor) they're a rheostat that eventually burns a wear spot causing that surge.

IAC motor

ok a couple of things to try one is loosen the throttle cable so it has a little play in it and then you can check for vacume leaks using carb cleaner if rpms change you have a leak

yes it could be. have fuel pump pressure tested, fuel pump pressure should be. (key on engine off) 1999 to 2000--with egr--41 to 47 psi without egr--52 to 58 psi,

Sounds like a possible vaccume hose leak?