About 3 months ago, I ripped out the auto tranny in my '02 Double cab, and installed an R150F 5 speed. Everything is great. It runs great. Fuel consumption is superp. Lotsa power. No problems, except that the engine will stall when coming to a stop with the A/C on. This only happens when the airvent mode is set to either defrost or foot/defrost. In either one of these two modes, the A/C comes on automatically in the '02 Tacoma.

I have unplugged the A/C pump so the magnetic clutch doesn't engage and put a load on the engine, but interestingly enough it still stalls. This tells me that it is not as a result of the load, but rather an electrical circuit problem.

Some of the common things as mentioned in my FSM, like PCV hose, MAF sensor, O2 sensors seems fine, and besides this only started happening after the tranny swap. I have left the majority of the automatic transmission sensors unplugged, except for the park/ neutral switch and the back-up light switch. I have re-wired the park/ neutral switch somewhat, so that I used the stock oem clutch switch at the bottom of the clutch pedal and hooked it up to the park/ neutral switch's neutral position. So, when I depress the clutch, the ECM thinks the auto tranny is in neutral, and it allows me to start the truck. Thing is, it probably also thinks that I am shifting from drive to neutral when I come to a stop as I'm depressing the clutch. Also, if I still had the auto tranny and shifted manually from drive to neutral as I would come to a stop, I'm sure it wouldn't have stalled, though.

So, as I'm coming to a stop, which is the only time it will stall, the A/C is on, but does not cause a load on the engine, because it's unplugged, I depress the clutch, and hence puts it effectively in neutral, I depress the brakes which causes a load on the engine, the TPS is closed and the RPM drops. The computer does not know what my speed is, since I have no ABS and the VSS is not hooked up.

The idle-up that one would expect just before the A/C kicks in, works fine when the truck is idling, but doesn't seem to wanna do this as I'm stopping - but this is difficult to tell. The idle-up process happens whether the A/C pump is unplugged or not.

What is going on? Hopefully it is something really simple, and I am just to stupid to think of it. Please help.