As I find useful tech over at MMUSA on FB I will be bringing it here so it can be found. Hopefully getting the tech here will be something the nuggets will realize makes it worth it to come here. So with that said, this is a post written by ?ça?úri Atilla Balkan;
As many already know, these throttle bodies have a Fast Idle Air Valve (FIAV) allowing coolant to flow in and out, warming the throttle plate. Since this is essentially a glorified thermostat, the wax wears away over time, and once itÔÇÖs stuck open, you end up having coolant constantly flowing in and out causing all sorts of issues. My 6G72 12-valve would run at 2,750 rpm on a cold start, then even out at 1,300 rpm once it hit operating temperature. In cold or high humidity environments, the FIAV helps prevent icing of the throttle plate, but where IÔÇÖm at, I donÔÇÖt have to worry about either of those.
I was determined to replace the FIAV, but $265 was a bit steep for something IÔÇÖm almost never going to need. IÔÇÖll probably still end up buying one at some point, but for now I ended up doing what a lot of 3000GT and Evo owners do; bypass it. Some folks block it off altogether, canceling out the IAC valve, which might be alright on a race car. Others reroute the hoses, and some Russian Pajero folks even went as far as dismantling the FIAV to tighten the plate shut with the spring compressed all the way. I just got the $19.99 special; a bypass plate which still allows the IAC to function while eliminating the FIAV.
The parts list:
ÔÇó FIAV bypass plate
ÔÇó FIAV gasket (MD614406)
ÔÇó Throttle body idle adjustment screw (MD614948)
ÔÇó Throttle body idle adjustment screw O-ring (MD608806)
ÔÇó Throttle body idle adjustment screw cap (MD614532)
ÔÇó Throttle body gasket (MD184046)
ÔÇó M5 x 0.8 x 35 bolts (4)
ÔÇó M5 x 0.8 x 20 bolt (1)
ÔÇó Anti-seize compound
ÔÇó Multi-purpose synthetic grease
After pulling off the throttle body assembly, I let it sit overnight in undiluted Simple Green Aircraft & Precision Cleaner. This stuff is aluminum safe and even Boeing approved! It came out looking like new the next day, but the 22-year-old Philips screws were still pretty much welded on. Managed to get two of them out with a pair of locking pliers but had to get the Dremel out for the others. The new bolts are 8 mm hex, although the short one I got ended up being a T-20.
The O-ring on the idle adjustment screw was shot, and since its plastic, I got a new screw just in case I had an unpleasant surprise. Mine never had a cap either, so I got one too.
I put everything back together, applying a bit of anti-seize on the threads (my favorite is Loctite N-5000, which is high purity nickel-based for nuclear powerplants). Dissimilar metals donÔÇÖt go together and the whole mess cutting out the bolts could have been eliminated with this stuff. Also put a light layer of grease on the gaskets.
Adjusted the TPS using a 0.65 mm feeler gauge and making sure I got no continuity (OL) on pins 3 and 4 before tightening it down, then put everything back on the truck. While it didnÔÇÖt shoot up to 2,750 rpm on a stone-cold engine this time, I let it idle until it hit operating temperature and adjusted the throttle body idle adjustment screw.
When cold, it now idles at ~1,250 rpm and at operating temperature itÔÇÖs at 700 rpm; just like it did when new. Turn the AC on, and it goes up to 900 rpm. Mission accomplished! No more "Whoa horse, whoa!!" the moment you put it in gear. ƒÿü
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