Idles fine, but stalls/dies at 2000+ rpm - long post, please help

[ATWork8803]

And as a matter of fact, I have gotten some more codes, but I don't think they're helpful:
P1616 - I think this indicates that I ran with something unplugged, which was most likely the egr valve
P2106 and P2110 - This indicates a "safe mode" where basically the gas pedal is disabled - I got this to occur twice by messing with vacuum hoses in an attempt to force certain conditions
P0107 - Manifold Absolute Pressure sensor low input - also likely caused by messing with vacuum hoses.

All of these codes disappeared without being cleared after a couple of startups

[ATWork8803]

It sounds like you're doing the compression test with the engine running - is that correct?

That is correct. How else do you get compression?

Edit: I just looked it up. Gotta disconnect the coil so it only cranks. Hmm. I was listening to the guy who let me borrow his compression gauge. So does that makes my results invalid? Or worse, could I have caused any damage??

Edit 2: Did a little more looking and it sounds like I just did a "running compression test," though much less thoroughly than a pro. One thing I read is that the running compression should actually be lower than static and at 200 psi, I'm running pretty high already. One source suggests clogged cat converter, which, along with my rattling exhaust could be something worth checking.

[avguy]

No damage done. Pull the fuel relay, remove all of the plugs, and have a helper crank (WOT, just a few times for each cylinder), while you watch the readings. Carefully note if some are taking longer to move up, and what the final readings are. Then you can repeat the test, adding a few squirts of motor oil into the cylinder to see what (if anything) changes. Sometimes the compression test doesn't tell the whole story, and a leak down test is also needed to complete the picture.

[ATWork8803]

Thanks, avguy.
WOT, as in with the pedal to the floor, or manually opening the throttle plate?

[avguy]

.... One source suggests clogged cat converter, which, along with my rattling exhaust could be something worth checking.

Many things could be the cause of your problem. But the fact that it went from running well to running very bad with misfires, in a matter of seconds tends to eliminate lots of things. Unless the cat broke apart inside, I can't imagine it causing such a sudden and significant change in the engine. A sensor failing, or a mechanical failure seems like the only likely suspects in your case.
I think you should do the standard compression test, mainly because you want to see how much of a difference there is in the cylinders, both final compression and how many cycles it takes to get there.

[ATWork8803]

Unless the cat broke apart inside, I can't imagine it causing such a sudden and significant change in the engine.

That was a big "unless," my friend! That's exactly what it was. Pulled my pipes and found a bunch of chunks. Pulled my cat and found it half empty and with the remaining honeycomb partially melted and broken. I fired it up with nothing but the exhaust manifold and it revved up to 4k with just a tap of the pedal and no problem to be seen!

Now the plan is to knock out what's in there so I can drive it while my new cat is on order

I will post up pics shortly.

[avguy]

Thank you for posting that information - good chance it will help others down the road!
Are you buying just the cat, or some of the other pipes behind it as well? Are the flange bolts rusted? No big deal if you weld and have that equipment. I recently had to replace the muffler on my '05, due to the mid pipe connector rotting out. I don't have welding skills, so getting those bolts cut out (without damaging the flange) was a RPITA.

[ATWork8803]

All the pipes, flanges and bolts look to be in good enough shape. All of the nuts (pipes and cat) were pretty well stuck on and the threads on one of the cat mounting bolts was damaged, but I managed to run a chaser over it. It *should* work out okay. Anyway, I've got a new cat coming so it won't be a problem or risk for very long.

By the way, I found a new cat for $165 at rockauto.com (let me know if such posts are against the rules on this forum) (RockAuto Parts Catalog)

At Autozone, the least expensive is $360

[avguy]

Must be nice to work on vehicles that don't spend their lives in the rust belt
No problem posting sources and brands for parts - it's one of the pluses of these auto forums to get that information out to other DIYers. I've always had good luck with Rockauto - they deliver the right stuff in a timely manner. Happy motoring once the new cat is on

[ATWork8803]

Thanks avguy. Yeah, Texas has got some bad humidity, but fortunately we don't get much (any...) snow and don't have to worry about salted roads!

I put my hollowed out cat back on last night. I took my muffler off before I tried to run it, though and I'm glad I did! It was full of chunks, dust, and water. I was able to dump out most by rocking it back and forth and beating on it with a piece of wood. I'm not sure exactly what's going on inside of that muffler, but I would dump it one way and get some chunks and dust, dump the other way and it would vomit water, and go back and forth like that and get something new every time (until I had notably less water inside and was no longer seeing any dust).
I tried it first without my muffler and it was loud, but revved beautifully.
I put back on the muffler and it sounded and felt so weak. It even stuttered a bit when I'd rev it. So finally I drove it and running around the neighborhood, it still felt like it wanted to cough just a bit, and many times it wouldn't want to change gears unless I quickly let off the gas - I expect that is a good symptom to watch out for when it comes to clogged exhaust: I got up to 4-4.5k rpm going along in 2nd or 3rd and it didn't want to shift until I released gas pedal (automatic transmission)

Anyway, once I got out onto a wider street, I got up to and held 70-80 mph and it must have blown out the remaining debris or at least shoved it to an innocuous location inside my muffler because it has driven like a champ since then - startup, low gear, high gear, no problem changing gears, etc.
The only thing I really notice is that the hollow cat rings like a bell at 2500 rpm and up. Not really loud and a low tone (kinda pretty, really ), but noticeable with the radio off.

I know I've posted an awful lot on this, but my mentality was that I would have killed to have come across a post like this one while I was researching my seemingly hopeless problem. Forums like this are a Godsend for people like me and any other thrifty DIYers without much automotive training!