Awesome! Good to know. I wish I would have pulled that little move before dumping ANY money on this. Would have pin pointed the O2 problem early :P
As for the O2's I got Bosches. I know they suck for spark plugs, but figured even crappy O2s would be better than broken ones.
Other than a 1 mile or less run home, I have not started the vehicle since the PARTIAL install. I will be taking it back to the shop for the full once over and new bung hole (?) so they can drop in the 3rd O2.
I will be limping back there on 2 O2s now though
Thanks again Kyle. I will update again after install.

 

Did they give you the old sensors? If not, ask for them back. Bosch O2 sensors are garbage IMHO. Unless they have improved their quality control over the last few years, I wouldn't touch them.

It is pretty apparent that your issue is with the sensor that is still installed. I would not have replaced the others. Especially the post-cat sensor which has nothing to do with engine fuel management. But I digress. Get that bung-hole patched up and you should be all set until those Bosch sensors take a dump on you.

 

**UPDATE**
So i got the bung patched and the last new sensor installed (after unhooking the old to drive back.)
With the butcher's bill reading Plugs, wire, cap, rotor, 3x O2's, and 2x Cats, I should have the best running truck here. Sadly that is not the case...
Problem on the Table: Still idles low (500 and choppy), hesitates and over revs out of first gear (feels underpowered and takes a 3-4k rev to shift), and I still smell heavy rich exhaust....

Noted Symptoms: There is a breather hole in the muffler under where the tail pipe is welded on. That hole has what looks like a black carbon paintball strike around it. The bottom of the tail pipe is also sooty (above breather hole)
The inside of the tail pipe is CAKED with carbon. It looks like a weapon that has been fired on full auto for like 12 hours.... It's so thick, it's actually building up around the rim on the outside!
Egine idlesand surges and chokes all at once. Read this outloud to yourself or a friend to understand what i'm describing (in the key of C flat)
"whim whim whim Unt whim whim whim whim whim whim whim Unt whim whim whim whim'

You like that for a symptom? Why dont you just make a recording, you may ask yourself. Well i barely post pics, what makes you think I know how to put a movie on here?

The Game Plan: Something is wrong. I have done what I hate, and what everyone advises against by throwing $700+ dollars at this with NO RESULTS. I am still convinced that my cat was plugged, and my plug(s) and/or wire(s) were bad.... Also at least one O2 was shot. While the maintenace aspect of those changes is nice, it hasn't helpped....
So i will fire the truck up and disconnect 1 wire at a time from the distributor. if it causes the truck to die/change drastically then it should = good. If it causes no real change then it = my problem. That will rule out the work I did. The cats are brand new with less than 3 miles total driving on them (or 4 minutes if you prefer).
Lastly, i over looked the problem of the red dusty build up on the EGR since I was busy throwing money at other stuff. I think I will swap out the gasket (6 months old BUT possibly over tightened when reinstalling for possible damage) and clean out the EGR one more time for S&G and because a poor seal there would explain the problems (vac leak for secondary air sys AND exhaust smell AND poor running conditions leading to heavy mix at plugs leading to missfires...)

What am I overlooking? What am i missing? What steps should I be taking to help myself out here? i am at a loss... is it possible the heavy exhaust smell is all of the build up in the system cooking off? Is there something that can clean it out (like a exhaust cleaner or pipe snake style tail pipe forward scrubber)?

As for the old sensors, I didn't keep them, and the shop chucked 'em.

 

Disconnect the exhaust behind the catalytic converters and see if your performance problems subside. When a cat self destructs, it can throw shrapnel back into the muffler.

I would also start looking at your grounds in the engine compartment just to be sure that you are not experiencing a weak ground...

Any codes yet?

 

No codes, but I will take her for a spin tonight following work and see if I can trip something. When you say disconnect post cat, do you mean the front or rear cat? Either will take the muffler out of the picture, but the front is the one I saw destroyed.
I will check grounds, but all were tripple checked when the TCEM thing was going on...
I will post any codes and findings tonight then.

 

Yeah, the point is to see if the exhaust is restricted further down the line. You have replaced everything up to the muffler so...

 

i have the same problems, minus the smell. it hesitates, and over revs from 1-2. the hesitation sucks especially when turning a tight corner onto the highway. i have no idea, I'm not to familiar with engine repairs yet. this thread was a great read, and may prove to be very helpful.

 

Here is a re-cap so you can get up to speed if you are just joining us in the search for why my Blazer sucks (at the moment):

Symptoms:
1) Heavy, raw, rich exhaust smell all around the vehicle.
Idles low and weak (chugging like its low on fuel).
In second gear the engine bogs down (loses power) and takes a surge in RPMs (4k or so) to shift.
Codes that tripped AFTER problem was noted:
P0300 - Random Misfire
P0410: secondary Air Injection System
2) After tune up, ran like new for 10 minutes then problems came back
Excessive fuel use (1/2 tank to go less than 30 miles)
When letting off accelerator, RPMs hold steady, then an audible whine like a turbo diesel engine is heard in exhaust for a second like it is blowing off built up pressure, then RPMs drop down like normal.
It is not as bad (other than exhaust smell) when cold (closed loop) but very strong after warming up (open loop).
Red dust like build up on ERG Valve, but not on gasket or engine.
Passenger side Plugs were all black, driver’s side were fine.
Still heavy exhaust smell.
3) Struggles to get into OD. Runs at high RPM in the gear before OD, but short of running it HARD to redline, will not shift.
Still has choppy weak idle.
Still hard to shift into second gear.
Still heavy exhaust smell.

Kyle’s Call:
1) Plugged Catalytic Converter (muffler shop seconds this, and after changing cat, Kyle = FTW!)
2) Sounds like a bad O2 sensor on Passenger side and exhaust leak is possible (previous codes [p0147 I think] seconds this. when pulled, the sensor was in bad shape, but was not tested , crack found on cat weld = leak[?]). Decision: Kyle = FTW!)
**NOTE** Bosch O2 sensors are not endorse by Blazer Forum as they are “garbage”.
3) Check Plugs to see if over-fueling is still occurring. Detach exhaust post-cat to see if problem lives in the muffler. Double check grounds in engine compartment.

New Parts Installed:
Plugs, Wires, Cap, Rotor, Front Catalytic Converter, pipe between cats, Rear Catalytic Converter, 3 O2 sensors. Replaced split vacuum line.
6 months ago I cleaned EGR valve, MAF Sensor, and Throttle body and ran a can of seafoam through the throttle body. A year ago I cleaned the fuel tank and changed fuel filter.

**NOTE** Searches for similar symptoms pointed to following problem areas:
Air Pump, Dirty IAC, Plugged injector/bad Spider, TPS out of whack, Plugged EIP Screen
I seriously hope I dont not have to buy my way through that list also...

 

I'm glad you enjoyed it (so far) and sincerely hope it proves helpful (even if only a little) in your situation. It's rough plowing through problem after problem, but as long as the forum is here, at least we don't have to feel alone

 

So I got a couple pictures to maybe help a bit. After letting her sit for a bit I cranked her up and let her warm up at idle. Then i ran the trottle up a few times and left it rock and roll at about 3/4 throttle for about 60 seconds. after letting it drop back down this is what i found at the tail pipe:

the goo looked much more black IRL, it is gel-like, like thick bad gas....


and here are a few vids that I hope help since i put them on my wife's youtube account
clicking at plugs
random idle issues
chugging at idle (sound sucks)
2nd gear woes...

Hope any of that sheds new light.

Muffler guy was busy tonight so i did not chop off the post cat exhaust stuff... I can sawzall it tomorrow and take it in to be welded up. did not get a change to pull codes. the drive I was on in the vid took me to the parts store, but they broke their OBDII reader... no dice...