This is a common “upgrade” for the std K Series engine and that is to replace the std 48mm throttle body and replace it with one from the MGF Trophy which is a 52mm (part No MHB000261 – search eBay lots about). Standard body in black on the right, 52mm on the left;
I got a second hand one and therefore took some time to clean it up and make sure it was dirt free inside and that the butterfly was clean and fitted perfectly;
Removal of the old body is simple, disconnect the body from the feed (large jubilee clips) from the air filter (note mine is a non standard filer – an ITG).
Then remove the pipe on the top of the body,this just pulls off and disconnect the electrical connector from the throttle position sensor at the back, you can see the connector and pipe being removed above. Then undo the 4 bolt that connect the body. Then disconnect the throttle cable, this just slides out of the slot on the rotating section at the front, you can see where the end of the cable engages in the picture below.
When it’s all off, take the time to get a clean rag and wipe away any dust / debris from the mouth of the plenum and wash through the air pipe to get any dirt and muck out, clean the surface where the new body will connect – Replacement of the new body is the same as above but in reverse.
DON’T FORGET TO RESET YOUR THROTTLE POSITION SENSOR
1 – With the engine off, insert the key and turn the ignition to position 2 (On) without starting the engine.
2 – Quickly but steadily press and release the accelerator pedal 5 times for TPS calibration, using all of the throttle travel as practicable. It is better to do this from the engine bay, using the cam on the throttle body, as this ensures you get 0-100% operation of the throttle, and correct calibration, If your throttle cable or mech does not give 100% throttle, calibration will be out. And potentially you will be wasting your time. This will trigger the ECU into the closed-throttle reference learn algorithm, which has it looking for the lowest measured static throttle position (the closed position). The throttle position calibration is a fixed definition from this point.
3 – Turn the ignition off, remove the key and wait for the ECU to power down (about 30-40s).
4 – Start car as normal.