My car trys to die when i slow down and stop but doesnt

Try cleaning the throttle body first, see if that helps, it sounds like the ISC is either dirty or the motor is slow with response time, it won't throw a code until it fails but you will get the symptoms you are having, a good shop should have the equipment to check for a slow ISC.

So my car has been not running for over a week. My ex i just found out put a mixture of water and dirt in my gas tank. I dropped my tank replaced the filter cleaned the tank and hose put fuel injector cleaner and gas in it and put a locking gas cap on it it starts but then dies afterca few seconds. I changed the spark pluggs today as well and they had quit a bit of oil on them i know i have a bad leak at the valve cover gasket how bad could this be and how do i know? I cant afford a mechanic so im doing this alone .... Help

Did you replace it he fuel pump while the tank was down? Dirt is very hard on the impellers of the fuel pump, the sock won't get it all. If there is oil on the plugs electrodes then your getting oil in the combustion chambers, check the crankcase ventilation system for a plugged hose, blocked clean air supply or malfunctioning PCV Valve, also check the security system, it may have been activated.