The engine controls group covers the link between the driver's right foot and the carburettor throttles, the accelerator pedal, the throttle cable and operating linkage, the choke (mixture) control, and the return springs that close the throttles. These components changed alongside the carburettor specification over the MGB's production run, so the correct parts depend on the carburettors fitted to the car.
Accelerator Pedal
The MGB uses a floor-hinged, organ-type accelerator pedal that pivots at the toe-board. The pedal pad, pivot, and return arrangement are simple and robust, but the pivot can stiffen or wear and the pad rubber perishes with age. The pedal acts on the throttle cable that passes through the bulkhead to the carburettor linkage.
Throttle Cable & Linkage
From the pedal, a throttle cable operates a relay lever and interconnecting linkage that opens both SU carburettor throttles together. Cars fitted with HS4 carburettors (used up to 1972) and those with the later HIF4 carburettors use different linkage and bracketry, and the cable, outer, and abutment details vary accordingly. Correct set-up ensures both carburettors open in unison and return fully to idle, which is essential for smooth running and a stable tickover.
Choke / Mixture Control
A dash-mounted choke control operates the jet levers on the SU carburettors through a cable, richening the mixture for cold starting. The inner cable, outer casing, and the clamp at the carburettor end are all serviceable items, a stretched or seized choke cable is a common cause of poor cold-start behaviour and a fast idle that will not return to normal.
Throttle Return Springs
Return springs ensure the throttles close cleanly when the pedal is released. Tired or missing springs allow the idle to hang and are a safety concern, so they should be checked whenever the linkage is disturbed.
The MGOC Spares range covers accelerator pedals and pads, throttle cables, choke (mixture) control cables, throttle linkages and relay levers, return springs, and all associated clips and fixings for the full range of MGB carburettor specifications.