The first thing I'd suggest is to take it to a local hobby shop. Car and truck engines can be a bit harder to get set properly since they tend to run hotter and are harder to get to. Not to mention you can't use a tachometer to help set it.

Otherwise the idle speed will mostly be set by using the transmitter trim. If it's too high try adjusting the throttle trim lower. You will likely then find that it is running too lean, I think. Most often I have found on cars and trucks that if they stall a lot they are set too lean. Try setting the high end needle valve at 3 turns out from fully closed. Then you can turn in small increments in from there until it runs good at top end. If the engine has a low end you should consult the manual for where to set the low end needle valve.

Your engine will run better rich than lean. I didn't say it would run well, but if the engine is rich it will run, usually, if it's too lean you canactually harm the engine fairly quickly.

Another thing to consider is that if the idle is too high and it's not moving the clutch may be set wrong or burned/glazed so it won't hold anymore.