I've been attempting to determine exactly what is was that the previous owner altered on my Monte when it comes to the exhaust. My confusion is this: The exhaust sounds rumbly, which is awesome because I like it like that, but I'm not sure what is causing it: does it sound more BA because the catalytic converter or the resonator has been removed? (It's certainly not those chrome tips ) There appears to be a welded, chrome straight pipe where one of these objects should be, and I simply couldn't figure out which was which on the stock exhaust. Can anyone diagnose exactly what has happened under here and why it would be causing the following Check Engine code "P0420"???

Autozone results:



Overall view:



Rear of welded pipe:



Front of pipe to O2 Sensor:



To.....resonator?




Yeah.....I'm kinda beginning to think that the resonator is still on and the cat is off.

 

Looks to me like the resonator was deleted with straight pipe, and the stock cat was replaced with a 'high flow' aftermarket mini cat (which is notorious for throwing the code you got).

Funny how they did all the work and left the stock u-bend- the most restrictive part...

 

Our montes are known for throwin that code also for the gas cap too. It's probably your exhaust, but a new gas cap could be a fix.

 

Which part is the ubend exactly? The dip right before the sensor?

 

In this pic first is your cat, then U bend / O 2 sensor ..



This pic is U Bend & O2 sensor..

 

AHA! Thanks mate! Do any attachments or deletions have to be welded or can they be bolted? Such as downpipes, mufflers..

 

First thing I thought of, too.

Gas cap will cause an evap code, not a catalyst low efficience code like he's got. It's the high flow cat.

Get rid of the U-bend, mount the O2 sensor sideways with a spark plug non-fouler stacked below it and walah, code will go away.

 

Here's a How-to for your code solution

Available at your local automotive store

 

MCF = Member's Helping Member's

Thanks Member's for your posts & Help to a MCF Member
===============================
Options/Cost & links below



, Catalyst back Exhaust System For use on 1999 - 2002
================================================== =

Borla Cat-Back Exhaust System Monte Carlo 2000-2005 00-05 14903 $973.71 <WOW- font AutoAccessoriesGarage.com<>
10% Off Coupon + Free Shipping!



Borla Cat-Back Ex...
$973.71
AutoAccesso...


Borla 14903 - Chevrolet Monte Carlo 2002 Exhaust Systems $894.61 - LMPerformance.com



Borla 14903 - Chevrolet M...
$894.61
LMPerforma...

================================================== ====

DupStep'in `Tyler, would enjoy hearing a sound clip of your exhaust when time permit's. Good Luck on getting rid of you code(s), and getting back on your highways of life..
Good Sounds 2 U

 

A Magnaflow downpipe will accomplish this for a reasonable price. You would need to have a flange welded back onto the straight pipe they put in place of the resonator though so it would bolt up to the rear of the downpipe. I installed one about a year ago and (so far) it has not set any codes. I was prepared to do the anti-fouler trick, but I haven't needed to.