2004 Mazda 3, with engine warm, engine at idle will suddenly drop in RPM and then immediatly surge. Sometime will quit running. Will do this while in park, stopped or while moving.

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

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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.

check for dirty fuel filter.

I Have a couple of questions. First question does engine surge when idleing cold? 2. Does engine start quickly without a lot of cranking, Cold or warm? 3. Do you have funny smell at highway speed, or after you stop? With out this info and your imput, I would only be guessing. I am retired mechanic of 25 years. and would like to help if u need me.

Have it scanned for fault codes as an indicator of the problem. If the throttle valve is gummed up, cold temps can cause it to stick. But diagnose first!

Sounds like the IAT (Idle Air Control Valve) or the MAF Mass Air Flow Valve

Dirt may have got onto the O2 sensor, this could cause a surge without the light coming on. Some debris may be on a sensor preventing the computer from making correct adjustments.....

Sounds like you have a vacume leak on your brake booster ....with engine running have someone press the brake while you listen on the driver side by the master cylinder the large vacume line going to the booster behind the master cylinder is most likely the vacume leak...and if so you can get what you need at your local parts store ...

This may been an ignition module or a MAF sensor, this car may need to be diagnosed using a OBD I computer code reader to accurately diagnose the problem.

Check your EGR or your Idle control Valve. This can cause a problem with your irratic idling

check your air mass meter or map sensor