don the next step is if you have problems when back peddle is a dirty I.A.C.V. that's idle air control valve, you can remove it and clean it and the air passage with spray carb cleaner, the iacv controls idle and also acts as a dash pot to over come a sudden mixture change at throttle closure, the computer looks at r.p.m. and eng. load from the map sensor and controls the air that goes around the the throttle plates, the iacv supplies air because the throttle plates are completely closed at idle. if that fails to correct the problem we'll have to go to step 3 good luck let us all know what happens....ted