I have a 93 SC4 with 142,000 miles on it. After the car is warmed up, if I set and idle I can smell strong sulphur smell. I have no center cat. Does anyone have excpearince with clogged pre cats? I have no CEL and car the runs great.

 

I know this subject has been talked about before, but dosent come up when searched.

 

From what I remember the precats cause some restriction to allow the engine to warm up quicker. The material in the precats heat and allow more heat and exhaust to flow. How do we know when its time to have them replaced. And I am assuming this is where my sulphur smell at idle with engine warm is coming from.

 

Either the cats are plugged or it's deteriorated inside. Your car only has 2 cats total.

 

I know it has 1 center cat. which has been deleted. Each exhaust manifold on a 4.0 has a precat , total of 3.

 

Anyone with real expearence would be great.