its the one behind the heater blower,when i start her up she starts for one second then stops,keeps doing that when it starts up black smoke comes out if i turn her off and try again it wont start keeps doing that,before this happend it sounded like it was fireing on three cylinders,it gradually got worse i changed the plugs as they were black,changed leads but still same problem just does not fire up,so i think its the ecu or metering unit any help please.