YES,but to make this easier ,lets say you have a second problem but need to find it.Now your 02 is marginal or even good.My way is to start with a new 02 first as this can make other parts look bad.In the brains of a car the 02 does alot and is a high wear part.80 to 100k on an 02 is alot .Yes some last longer but starting with a new 02 for the most part puts the car in fuel control.Then if something else is wrong you can continue from there. You will find most of the time that the car is ok now.
PS that smell is your cat overheating and maybe starting to melt.
Cheapest part first
Rich
MY 91CE had bad fuel injectors when i bought it and instead of buying 6 new ones i tried to find the bad one.Well ended up replacing injectors to late and my cat is now melted.

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88 300E White, sold 9-04
88 190E Black 2.3 sold
90 300CE White, Grey sold 12-24-04
92 400E White,Grey Sold 5-06
90 300CE 91K Signal Red,Black Sold 2007
1989 300CE Smoke silver,Tan Sold 1-08
1993 300E 3.2 M104 motor
1991 300CE White,Grey
1994 E420 beautiful car,gone to new home
1994 E320 Smoke an Parchment.Beautiful car