I have a 2003 S-Type, 3.0V6 auto, which runs fairly well other than at c. 1,000 revs the needle will vary back and forth to/from 1,200 revs.
This is accompanied by corresponding whir from somewhere (I know nothing about most things and even less about cars)
Acceleration at these low revs can be delayed / sluggish unless I put my foot down (which is rare) and the car will happily fly along at higher speeds/revs.
Any assistance would be greatly appreciated, obviously the car s not worth much but it is all I have.

 

Two things to check before going any further: battery voltage and fuel pressure.

With the ignition in the OFF position for at least ten minutes, there should be a minimum of 12.6 volts across the battery terminals. If not, try charging the battery overnight and retest to see what the voltage is. If it's still not 12.6 volts or higher, the battery should be replaced.

Fuel pressure should be between 3 to 5 bar, depending on throttle position. Refer to the Workshop Manual for the procedure to check fuel pressure at the engine fuel rail.

 

Many thanks, I need to find my multi-meter but have ordered a fuel pressure gauge test thingy as no local mates have one.

 

Make sure you also check for vacuum leaks. fuel trims should be looked at also. The V6 has a few known vacuum leak areas. search this forum for threads.

 

Does it happen no matter what gear? And fluctuate when parked?

 

There is minor variance when parked, i think the OBD thingy said it was around 780-800 revs, as it's an auto should I try it in the semi-auto gears?

 

Yes. The number shown is the highest gear you're allowing (though it will avoid damage should you try something daft).

Fuel trims may provide info, too, as has been posted already.

 

Many thanks all, I will attempt to work through the recommendations in order - I am just awaiting delivery of the fuel pressure gauge and then will make another effort to find the fuel rail (yep I am that clueless)