when i let go of the gas it drops to about 100 rpm then win i get to like 5mph it dies

spark plugs maybe or somthin else??? plz help

 

do a search on "idle problem" and tons of these issues are here. i bet that your AC isn't on? if you turn on your AC it will be fine. some people say it's the throttle problem, clean it it helps, etc...

 

Its a problem on the GS400...i believe. The quick solution is what Rominl said to do....turn on your A/C.

 

Clean your Idle Air Controller valve, your Throttle Position Sensor, check/replace your sparkplugs, check/replace your O2 sensors, clean up your throttle body, clean your MAF and intake (go to the dealership to do it if you are scared), check your fuel pump or fuel level sensor.

When all else fails, turn on your aircon. It should run even though with very low rpm.