Hey there everyone , i have a 91 cavalier convertible with a 3.1 multiport and i have that rotten egg smell after its been running for a while , i replaced the oxygen censor last weekend and it still does it im hoping i dont need to replace the cat , i was just wondering if anyone has any idea?

Thanks ahead of time for any info.

Pino

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Pino
91'Formula
LB9 305 TPI 5-speed
http://www.geocities.com/MotorCity/Garage/5654/mur91.jpg

 

sorry to say but i think it's the cat.

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-=ICON MOTORSPORTS=-

 

Pino,

The "rotton egg" smell is caused by high sulfur dioxide emissions. This is generally caused by a catalytic converter that is overheated. Either your fuel mixture is excessively lean, the exhaust is restricted, ignition or valve timing is really late, or you have an air leak into the exhaust manifolds. Excess air in the exhaust can be from either the AIR diverter/bypass valve malfunctioning or a leak in your EGR tube or aspirator tube ro the cat (many newer engines don't have the aspirator tube, but I'm not sure about a '91).

It's also possible that the engine is being operated lean from low fuel pressure, fouling injectors, improper air adjustments, or intake and/or vacuum leaks. If you are not getting a DTC indicating you are running lean, you can probably assume you have excesive air in the exhaust or a restricted converter/exhaust.

The excess air can be verified by an exhaust gas analysis, or you can verify the proper operation of all the A.I.R. components.

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Later,
Vader
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"Make Me Bad"
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