I recently failed smog. NO engine light and no rough idle. Car runs great! Has 194K miles on it and has been maintenanced regularly along with oil changes every 3K miles. I failed smog twice! The first was because my timing was jumping around and the emission was running rich (per smog tech). Some module was replace and synced with the computer and the timing was back on the money at 10 degrees. Told by mechanic it should pass now! WRONG, the emission failed. I have attached my report any suggestions I can give to the mechanics?

 

You might want to look at this thread.

https://www.clublexus.com/forums/gs-...e-problem.html

There's some pertinent info there as to what could be causing your emission issues.

 

Thanks for the info. I didn't realize I have two catyllis on this car! UGH. The mechanic is gonna change one out and hopefully this will solve the problem. I think the EGR and tuneup along with timing have all been checked!

 

Finally Passed Smog! Initially the timing was at 26 degs BTDC. The mechanic checed timing marks and found both cam and crank marks lined up ok. He checked the trottle position switch and found to be out of spec. Was not at idle when the throttle plate was at idel. They adjusted the trottle switch now the computer has gone into timing check mode and they were able to set timing to spec 10 degs. Went to Smog check again and it failed for emission! Too Rich! Went back to the shop and they found that the Catalyst was bad. Both were bad! Changed one and this shop had a smog probe so it passed and I took it to the California star smog and yes it passed
I'm new to this site and not sure where to ask why does the car come with two mufflers and two cats???

 

Congratulations! Glad to hear your were able to pass smog

As far as your question is concerned, I'm not sure as to why the exhaust system is set up the way it is. Maybe someone more knowledgeable about the car can help answer that.

Anyhow, welcome to Club Lexus

 

Congrats on the Smog Pass! & Welcome to CL!

I believe the 'dual exhaust' was done primarily as a marketing / sales tool for these cars to compete with other high-end cars. Feature is a 'must have' at the original price point. Supras, and many aftermarket exhausts are single exit (w/ bigger pipes), so I do not think there is a huge performance benefit. Looks nice though!

Dealer perspective: 'So that you have two to replace!'

You'll have to post up some pics of your GS, mine has found its way to only 101K, so I to learn what's coming from others with higher mileage