Re: sulphur smell at exhaust (archive)

The rotten egg smell, generally is due to overheating the cat usually from an overrich fuel mixture or incomplete combustion. If it hasn't burnt up your cat already it will soon. That smell does not necessarily mean the cat is bad though. Check the usual suspects for overrich mixture first, temp sensor for ECU, 02 sensor, AFM/AFM adjustment, cold start injector, vacuum leaks, etc... A fouled plug can also cause problems like that since that cylinder will be dumping unburned fuel air mix into the exhaust which the cat will try to burn and overheat itself.

Matt
Maximillian Importing

i noticed tonight that my 88 M5 has an awful rotten egg smell emitting from the tail pipe at idle. i thought immediately of the cat, but after a little search on the net, saw quite a few other problems that could cause this. so is my cat most likely bad? (114k miles on original cat). it would seem from my search that even if the cat is bad, there has to be an underlying problem to cause this. i also gathered that the car may be running too rich or has an ignition problem. any experience with/ troubleshooting tips for this situation is greatly appreciated. - jeff heller

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