Please could you help with this condition:
At idle, the revs used to be rock solid at ~ 950 rpm when warm and a little higher when cold. Now the revs drop to about 600 rpm for a short time then rise to 1,200 rpm before settling to ~950 rpm, for a short time ... and the cycle then repeats. When I pull away from lights, there is a hesitation between accelerator pedal depression movement and response from engine, which wasn't there before. When I slow to stop at red light, I depress the brake pedal and the resistance felt after initial movement is much less ... the pedal travel is further for the same braking effort.
Everything is original from 1998, I know this because I've owned it from 6 months old. Full service history with Audi. (Original coil packs). Recent fuel filter and associated pipe to tank fitted. Last 5 years or so, run on BP Ultimate 97 RON petrol. Engine with Mobile 1 0w40 from 3rd service. Car covered 107,500 miles of mainly town driving.
No codes as yet to help.
Appreciate any advice on common / usual / most likely faults.