campbmic wrote:Thanks for the reply!
When you say "replace the incident upstream" rather than use the spacer, do you mean replace the catalytic converter?
I took a rubber hammer to the exhaust and all the heat shields seem to be secure, nothing moved around or made the noise I hear when the truck is on. Also the noise seems to dissipate when the revs go up. When the engine goes back to idle the noise seems to start back up.
The noise sounds like someone shaking a spray paint can, or like a bad bearing. When a catalytic converter goes bad is there typically a noise it makes?
I'm charging up the ipad to get a video of it, so Ill post that soon.
Thanks again for the help!
Yes, I meant the incident catalytic converter. The noise will be a rattle coming from the inside of the converter shell.
Many upstream converters on these vehicles seem to fail right after a misfire condition, especially those due to a failed coil. The coil fails and allows unburned fuel to enter the exhaust stream, into the upstream converter. Next thing you know, catalyst codes trigger.
The ECM triggers catalyst codes based on the response from the upstream and downstream oxygen sensors. Since the downstream catalytic converters are located AFTER the rear oxygen sensor, they are not monitored and can only cause catalyst codes if they are clogged, which is not impossible, but rare. I eliminated my downstream converters, replacing them with Doug Thorley mid-pipes. Technically these are for "off-road" use, as it is considered as "tampering with a federally controlled emission device," but it passes inspection where I live (it may not pass in other areas or states, however, especially California or NY State).
Debris from the upstream converter will not end up behind the downstream converter, unless the downstream converter is gutted (someone removed the catalyst substrate from inside the converter). The debris in the "box" (which I assume is what they are calling the "Y" junction of the front pipes to the single pipe that goes into the main muffler) could be from the driver's side, downstream converter. Obviously, the only way to know what is rattling inside the "box" is to disassemble the exhaust and inspect it. As far as the downstream converters, you can't inspect the rear side of the substrate unless you have an endoscopic camera. One could simply hold the converter/pipe assembly and tap it on a hard surface to see if any debris falls out of it. The front side can be inspected, which would catch any debris from the upstream converter. If you're replacing the upstream converter, you have to remove the downstream converter, anyway. I can see the shop's view point, however. Since you've already have replaced the passenger side, downstream converter, and currently need to remove the driver's side, downstream converter in order to replace the driver's upstream converter, it would seem like a good idea to replace the downstream driver's converter, as well. It's not a bad and for them it covers their butt in case you decide to not replace the downstream converter and end up with problems later on with it. Again, as a reminder, make sure you read the converter's warranty; most will require replacement of the oxygen sensors to uphold it in the case where it needs to be replaced within the warranty period.