Weber 32 DRT 8 carb sticks on full throttle

[Pickup]

Hi folks,

Looking for some help / advice on a Weber DRT 32 carb. Vehicle is a 1985 Renault 5 Automatic (1397cc) with 32,500 miles had been laid up for 15 or so years but in use for the last 2 months (1500 miles).

Intermittent fault which occurs if full throttle is applied (ie accelerator pedal is fully depressed) for example when overtaking (which doesn't happen very often), pulling away at a roundabout or going up a steep hill. Engine "races" - revs don't drop when throttle is released (no rev counter but I'd estimate 4500-5500 revs). If neutral is selected and foot removed from accelerator pedal then (usually*) after 2-3 seconds the revs drop to normal idle speed.

Problem occurs more frequently when engine is at normal operating temperature.

• Sometimes the ignition needs to switched off (vehicle stopped at side of road/ car park) for 3-5 minutes.

The Haynes manual for the car refers to "additional enrichment provided by a pneumatic device" under high load or acceleration which opens a "valve" to allow additional fuel in to enrich the mixture. I suspect this valve or the "pneumatic device" is sticking but so far am unable to source any significant documentation on the carb - the Haynes manual does give some info on basic setup (float level, fast idle).

Have given the carb a blast of CarbCleaner with no appreciable difference.

Thanks