My stupid brother-in-law left me his keys, he was apprehensive on his return only to find it okay. Then a week or so later when the weather improved he complained of a fishy smell.........................I hung a couple of part cooked smoked kippers inside his heater matrix.........alas he found them but broke the string

They were still in it when he sold it!
What car is it?
Sunvisors filled with confetti, crisps and rice works well.