throttle body block plate...

i'm sure many drivers using fuel injection engine do had some difficulties with unstable rpm whenever the aircond kicks in... this is because the ISC (idle stepper control) unit which is located below the throttle body has damaged... particularly for MMC engines, the ISC unit breaks down frequently and it is expensive to service in long run... ISC repair kit can be bought from spare part shop... it consist of a few plastic gears inside the ISC unit...



however, this does not solve the melting problem of the ISC chip because it rests on the hot coolant hose running at the bottom of the throttle body...



hence, they came up with this alternative solution...





it blocks the coolant passage in the throttle body... means u no longer run coolant into the throttle body as it is deemed unnecessary in hot tropical countries... the plastic ISC chip remains and it activates the stepper function whenever aircond kicks in... the disadvantage is, at Rm150 per unit it is rather expensive and it is still made of plastic and it does melt or damage sooner or later...

one more solution which always been mechanic's recommendation is to use Toyota AE101 FICD (fast idle control device)... this electrically actuated valve can be adjusted to allow any given amount of air leaked into the engine to bring up the engine revs up to desired speed...



on my current setup, i have 2 units of FICD to control the aircond idle revs and cold start idle revs individually... with this, the ISC unit can be removed all together...

i had some spare aluminum plate lying around left over from my FYP project... took out my old throttle body, removed the ISC unit and did some measurement...



sent the measurement and the aluminum plate to machine shop and this is what it came back...



i made a paper gasket to properly seal it air-tight... i also swapped the notoriously-difficult-to-remove screws and had them replaced with allen key screws...