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Discussion Starter #1
So, I've been struggling with an exhaust rattle for a few weeks now and after replacing gaskets and bolts and adding a couple of additional exhaust hangers, today I realized that my catalytic converter is rattling. Apparently, the insides are coming apart. I've already gutted the pre-cat and I'm wondering if I can unbolt the center section of the exhaust and gut the main cat also. I can't really afford to replace it right now, and if I did, I would not get a universal one since I'm not a welder and have had bad luck with using parts store couplings and stuff to bolt in a catalytic converter. I have a couple of questions. First, if the main cat is gutted, will the PCM still get readings from the O2 sensor and operate like it's suppose to? Second, I've noticed that the part number for the center pipe that includes the main cat is the same for the 3.5 and the 2.8, so I guess I can use the center pipe from one of the 2 4 cylinder Colorado's at my local U-Pull lot.
Thanks for the help.
 

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Discussion Starter #3
I was thinking about using a piece of rebar, but I was also wondering if a piece of PVC pipe would work. I've got PVC pipe in several sizes on hand. Let's do this and compare notes on what works best!
 

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Discussion Starter #5
I'm talking about the main cat, not the one in the manifold. That one was gutted years ago. The main cat has a rattle now. There's no getting a drill to that one. I cut the pipe in front of the cat and used a 1" spade bit to clean it out. My problem is that I broke the bolts connecting the center pipe to the back pipe with the muffler in it. There are stud in the rear pipe and they both broke off almost flush. The have a little bit of a head on them, but it's not something you can put a wrench on. I can't tell if they are welded in or if they are splined and pressed in. I don't have really good small bits for drilling onto this really hard steel, so I'll be going to get some tomorrow. Looks like a long day of drilling holes moving up from a small bit to gradually larger bits. Obviously, nobody is open today since it's Thanksgiving. Time to put away the tools and get cleaned up for the trip to Dad's house for the big family gathering!!
Gobble Gobble!!
 

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Discussion Starter #7
Yeah, unbolting the down pipe and pulling out the O2 sensor, will give you plenty of room to get all the stuff out of the pre-cat. That should be a pretty easy job if the three bolts holding the manifold to the down pipe come out without a lot of trouble. I hope your have a couple of long extensions and a deep 15MM socket. Spray them down with some liquid wrench (tested best for penetrating rusty bolts) and you should be fine. Have fun!!
 

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Discussion Starter #8
All done. What a mess! Broken bolts, fighting with those "rubber band" exhaust hangers, drilling out those splined studs, on my back in the driveway wrestling with those exhaust pipe sections, Constantly jacking it up and down to move jacks and jack stands out of the way.... Worked on it about half the day yesterday and half the day today. It almost kicked my butt!! Im getting too old for this crap!
But it's done. The annoying rattling of the catalytic converter is all gone.
 

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Old Guy how are the O2 sensors working since the double cat delete working out. Are you getting a check engine light ? Can you scan the fuel trims?
Fingers crossed for you.
Luck
 

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Discussion Starter #11
After driving for about 30 minutes the CEL came on. P0420, as expected. I'm going to try the spark plug anti-foul trick and see if that stops the code, but I'm very interested to look at some live data and see how the computer is handling the lack of good feedback from the O2 sensors. I'll let you know what it looks like.
 

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Discussion Starter #13
No real change when I deleted the pre-cat. Since the O2 sensor is AFTER the pre-cat, there's no way for the "brain" to know if it accomplished anything or not. I've never figured out the purpose for that pre-cat. The "brain" usually measures the exhaust before entering the cat and after and determines if it's working correctly or not. That's my understanding anyway. The pre-cat gut made the exhaust sound different, but that's about it. I did the pre-cat delete based on posts on this site that promised increased HP as well as increased MPG's, but I don't feel that I experienced either. The main cat was rattling terribly loud because it was falling apart on the inside. At 225,000 miles and this not being an inspection state, and that all combined with Christmas right around the corner, I figured I'd knock the guts out and and possibly spend the money to install a catalytic converter later if this fix causes any issues. I purchased the 2 spark plug anti-foul adapters, but have not installed them. The P0420 code came on last night during a 45 minute drive to go babysit my 2 grandsons. I had my scangauge II plugged in so I immediately cleared the code. It came on again on the ride home and I deleted it this morning. A lot if in-town driving today and it hasn't come on again. I loaned my code reader with live data to my son who's having some issues with his F-150, so I don't know what fuel trims look like. Very low readings prior to gutting the cat, so I'm curious to see that it's doing now. I do feel a increase in "PEP" and from just looking at my gas gauge an estimating, I'm hoping to see an increase in MPG's also.
I'll keep posting and I look forward to checking fuel trims before an after adding the little anti-foul fix to see how that works.
 

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Discussion Starter #14
When I cut the pipe, I cut it just before the main cat and drilled out what little bit of "stuff" was in there and dumped it out. If I had it all to do over again, I would probably have gut the cat completely out, or at lease paid attention to where I made my cut in the pipe. The exhaust adapter and clamps for putting the pipe together right now are working great, but they are in a tight spot between the frame rail and the torsion bar and right above a cross member, so tightening those clamps was a little tedious because I could only get a couple of clicks on my ratchet. Also, I think cutting out the cat and replacing it with a straight length of pipe would provide a smoother path for the exhaust to flow through instead of creating an expansion area to make a congested area in the exhaust flow.
Probably not a big deal. It's not a racecar, it's just a work truck.
 

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Discussion Starter #16
It's just been a few days. I'll be filling up again later in the week and I'll check mileage. It feels a little more responsive, but nothing incredibly noticeable. Last time I bought gas, the low fuel light was on and the gauge on dead empty. I I put 18.5 gallons in and the mileage I got on that tank full was 275. That's less than 15 MPG's! I was at 3/4 of a tank when I gutted the tank, so I'll have to do some pretty high-level math to determine what my increase in MPG's will be. My best calculation based on getting 225 miles out of the current tank full of gas, I should see at least a 2 MPG increase. Hey, I can live with an extra 36 miles out of a tank full of gas! Cobalt Drill bits, muffler clamps, exhaust pipe adapter, two spark plug anti-foul adapters an a 6 pack cost me about $50. So, I'll make that money back on the money saved on gas in about a week!! That's not a bad repair, if you don't consider your time to be worth anything!! Hey, it was a long weekend! I also hauled 3 loads of crap out of the garage to the dump, Cleaned out the bed of my truck an my utility trailer an hauled off a lot of that crap to the dump and cut up and splitered a lot of scrap wood for the fireplace, and got all my tools organized in my truck tool boxes, and repaired the pump on my pressure washer!! It was a very productive weekend! And I managed to spend most of thrusday - Thanksgiving - with all my family including all 3 of my grandchildren! Grandchildren are the best! Granddaughter is 5 years old and grandsons are 4 years old and 18 months old! Oh, and my youngest son got engaged over the weekend, so maybe he'll start a family soon and give me some more grands!!
 

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Discussion Starter #18
Low Fuel light came on today. Filled up my tank and checked my MPG's. 15.25 . Pretty depressing. The spark plug anti-foul adapters have kept the CEL from coming on though. And, I was down to 3/4 of a tank when I gutted the cat, so maybe next tank will give me a surprise! I'll let y'all know.
 
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