I did a IACV and throttle clean, but the problem is still there. Someone said it could be a problem from the fuel injector. I have no problem during driving except mild shake on idle. so it seems it may not be from the fuel injector. I knew the fuel injector is a ofen issue for the Nassian V6 engine and I will replace all of the fuel injectors later. How about the Distributor? Someone said if the distributor got the problem your car would be up and down during driving. Now my van is smooth when the speed was below 60 miles. if the speed is above 65 miles, I could feel my van is kind of up and dwon. Hope to see more comments. Thank!