@db4960 because I do not know is there an imminent failure or can one drive on and turn up the radio?
The reason we should not close the discussion is because we’re not here for our own entertainment. We’re here to help people. And as of earlier today the OP was still actively reading the thread hoping for ideas, as indicated by his post.
Db, I am not in the habit of walking away from someone asking for ideas simply because I think all the options have been offered.
Anyone who is here for his own self-satisfaction rather than to try to help people is free to leave.
mountainbike
I’ll go a little off topic here . . .
Please don’t lecture me
Both my parents were teachers, and some of my uncles and aunts were also teachers
I don’t need any more lecturing . . . I’ve literally had enough to last me a lifetime
Than don’t propose to close threads where the OP is still actively seeking answers.
Let’s let our disagreements end here and get back to seeking solutions. Fair enough?
First, I am here for my own entertainment, and this is it! 
Closing the thread at this point would be silly and suggesting it is surprising.
As for the problem, I’m on the loose heat shield assumption and if it is ever figured out for certain I’d like the thread to be here so that the OP might report back on the ultimate outcome.
mountainbike
Fair enough
No more disagreements on this subject
At least one person is honest enough to admit that this forum has entertainment value . . . !
Thank you for the chuckle, db. You have definitely lightened my load.
Thank you everyone for your thoughts! I believe that most of you know that it’s not necessary to demand that everyone end this discussion in order to end it for oneself. All you have to do is stop reading it. Making repeated demands to end it sounds like censorship and is controlling, imho.
So, here’s the update: Two days ago, I left the car idling too long. The intent was to be gone for less than a full minute, but it ended up being more like 10-15 minutes. WHen I got back in the car, the “service engine soon” light was on, so I drove straight to mechanic #2, thinking it was definitely the CC, and told him to go ahead and put on a new one.
It was too close to 5pm for them to do it that day, but he checked for a code and said it wasn’t the CC. He said he’d have to do testing the next morning. The light stayed on for the drive home, and that night when I made a short run about a mile away.
The next morning (yesterday), I got in the car to take it in to the mechanic, but the light wasn’t on.
I decided not to take it in until consulting those who have no money motive, here at Car Talk.
So, now I see that “mountain bike” has used a clamp. The thing I assume is the CC is too big around for most clamps, I think, but I’m going to go to HOme Depot to see what they have. I’m also thinking about duct tape, but maybe the CC gets too hot for that.
And yes, it is entirely possible that I misunderstood things that mechanic #2 said. Maybe the thing I’m seeing is really the heat shield that ENCLOSES the CC?
Yes - the point about the hose clamp would be on the thought that the only thing making noise is the heat shield. They’re just thin sheetmetal and usually spot welded. A little bit breaks off and it gets loose and with the right resonance from the car it sounds like a rat is down there with a miniature machine gun. If it is just the heat shield a decent local muffler place would likely tack it back in place for peanuts.
DO NOT use duct tape. It absolutely gets too hot.
Do you happen to know what error code was that the mechanic pulled from the computer? It would look like “P0123”
he told me the code but I’ve forgotten.
I will NOT use duct tape on it 
I work tomorrow but will take it to a muffler shop on Monday-assuming it doesn’t break down before that- to see what they think about fixing the heat shield. That would be great if that fixes it, as I can pay with peanuts.
Make sure you bring the original Planters brand peanuts
Worm drive hose clamps are easy to “daisy chain”. That’s what I do.
But it sounds like you have more than a rattle. Do you have the actual codes that the shop saw?
Okay, around 1pm, I headed to the nearest muffler shop, opting out of going to Midas a little bit further away, but right off the interstate. One thing that struck me as VERY unusual was that the guy didn’t get uneasy or angry when I followed him into the work bay. In fact, he was talking to me as he walked into it, so he was essentially “inviting” me in.
After he lifted the car, he knocked on the cc and told me that I had to get a new one, and that clamping it wouldn’t work. He took me over to a pile of old converters, showing me the insides, and a bucket of stuff that looked like silvery charcoal, that he explained was the broken up honeycombs and bits inside converters that he saves because he gets paid for it.
He explained what the converter does and why he thought it wasn’t just the heat shield, and didn’t give me the “you’re going to end up on a dark lonely hwy. waiting for a tow truck if you don’t get it done today” schtick.
When he told me the price, which was less than everyone else quoted, I decided to go ahead and do it.
WHen he took it off, he showed me the loose honeycomb inside, explaining that I caught it early enough for the “check engine” light not to have come on yet.
The whole thing took less than 20 minutes, which was surprising since the other two mechanics said I’d have to leave the car with them because the repair takes “half a day”.
Total cost- $265, which was $200 less than mechanic #1, and $100 less than mechanic#2.
SO…
My HUGE thanks to ALL of you, and especially to ‘mountainbike’ and ‘cigroller’ for suggesting the clamp at a muffler shop, because, although I did end up getting a new cc, you saved me money AND time.
And, btw, “mountainbike”, I’m assuming you ride one. I road a Cannondale mtn. bike for years, then got my current Giant ATX 880, which was a much lower end bike than any of the bikes owned by guys-or the few other females- I used to ride with. (What? You’ve only got front suspension??)
I busted my kneecaps open on rocks a few times, and don’t heal well anymore, so I quit riding off-road. I miss it, and hope you’re able to ride off-road well into your 70’s!
I rode hardcore for years. The last bike I built, which I still have, is a Giant ATX-AL1.75 (pro frame), triple-butted ovalized aluminum. The frameset weighed 3.5 pounds. I built it up with a combination of XTR and LX derailers shifting a 24/36/48 ring set and a 12x32 cassette on an old fashioned bottom bracket, Sakae 8005 MCU shocks, XT hubs with Wienman rims and Tioga Psychos (old style). The stems were Kalloy Uno and the seat was one I pulled from a ProFlex that I had.
I’m laughing to myself as I type this, because everything on it is either no longer made, is obsolete, or the company is no longer in business! It was a long time ago. I stopped riding because of degenerative disc disease.
I was riding when front suspension was invented, and the only full suspension bikes were ProFlex and MountainCycle. Trek was the first to mass produce full suspension, and the design was, by today’s standards, really hysterically bad. My son is now an active mountainbiker and competitive roadie in southern CA.
@APMork
What state do you live in?
Does your vehicle have California emissions?
@the_same_mountainbike
I was in high school when all this suspension stuff was starting. The first Trek full suspension designs were really hysterically bad by the standards of the day!
Good point. Even back then they were considered pretty scary.
Sorry to hear about your kneecaps, by the way. My worst was on a descending singletrack, when I did an endo and wound up crumpled in a pile of boulders with a torn up rotator cuff, two sprained wrists, a chunk out of my elbow, and a busted helmet… thank God for helmets!!!
I miss riding too. I wouldn’t trade off one single second of my time spent on my mountainbike.
Maybe I’ll next figure out how to get notifications of emails to these threads.
In the meantime, mtnbike, I thought you were responding to “macfisto” , until I saw “kneecaps”. I suppose it’s actually the joints, rather than the actual bones, but I have plenty o’ scars on those knees to show for it. MY regrets are not riding more off-road, and maybe racing so I could get better at it and not end up crashing out of fear.
When front suspension came out and I got my Giant, all the guys were raving about how GREAT suspension is! But, when I was on bumpy trails, it felt like I was riding a pogo stick and was going to bounce right off the trail. Several adjustments didn’t help that. And it didn’t help that I could only get two fingers on the brake levers because the lever is so far apart from the handle.