What can be the cuase of the strong exhuast fumes coming out the muffler. I am planning to clean the egr but can this be the cuase? or maybe the accel ignition or the Hypertech programmer?

 

Whatever it is I am getting bad mpg too and think it is all the cuase of the same thing.

 

Well thanks for everyones reply. I never changed the cat so I am going to and maybe that will help. Now I am looking for one and and wondering which one to get. I saw car sound cats, magnaflow, catco, which ones have you guys heard that really improves the performance. I think the cat I had went out after I put the gibson exhuast. All the backpressure got released and did it to the cat.

 

Are all the pipes the same diameter?

 

which pipes are all the same?

 

Ah *sarcasm*... I must have missed this post somewhere along the way.

Anyway, the smell normally associated with a bad cat is a strong rotten eggs type smell. If its a strong gas smell, then the problem most likely isn't your cat, but a very rich fuel mixture, which if allowed to go unchecked, will ruin a cat. A simple test at an exhaust shop can tell you if your cat is clogged or otherwise not functioning. If it wasn't working properly (on a '96+ vehicle - should really specify which blazer we're talkin' about here) it will throw a code for insufficient catalyst something or other (if I really wanted to I could look up the specific codes).

An exhaust system will not harm a cat.

When it comes to aftermarket cats, they are pretty much all the same. The 3800 community (Grand Prixs, Bonnevilles, etc) have had very good luck with Magnaflow (Catco - same thing) cats with no problems throwing codes on the newer OBD2 vehicles (again '96+). Get one that has the SAME exhaust size as the current one. The aftermarket elements will outflow the OEM one they replace so I wouldn't worry about it. If its on the '97, then GM should replace the cat for free if its bad. I believe that the emissions controls are warrantied for 10yrs/100,000miles, but you'd have to contact your dealership to find out for sure. If it is under warranty, you have them look at it and if you are wrong and the cat is still good, I'm sure they'll charge you their time to diagnose it.

 

Sorry for not being clear. I was wondering if your after market exhaust inside pipe diam was larger than the stock.

 

How long since a tune up? Ever replaced the oxygen sensors? Im assoming you have a gas smell based on the fact that you were going to clean the egr.

It could also be due to the programmer, if it adjusted your air fuel mixture or timing you may not be burning clean.