It's a 2001 Blazer, 2WD, standard transmission. Sorry for not posting this earlier, I have just been back and forth trying to figure this whole thing out and trying to secure a ride for work, my brain is a little overloaded at the moment.

UPDATE:

I went ahead and replaced both the MAF and the Crankshaft Position Sensor, and nothing. When I unplug the O2 sensors, it will idle fine. I can rev it up while it sits in neutral all day without any issues, I can even go in reverse without a bump or a noise. The moment I stick the thing into first, it dies almost immediately. A couple of times I was able to get it to start going, and made it around my block without it dying, but any time I went over 1500 RPMs, and every time I changed to a new gear, the engine will rock back and forth the moment I touch the accelerator. If I get it in gear and leave the accelerator alone, it will move without a bump, but touching the accelerator at all is a nightmare.

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Short version:
Rough idle, sporadic sputtering during acceleration (usually smooth in 2nd/3rd gear, sometimes not), and I smell fuel, all after I had the catalytic converter removed.

Fault Codes:
P0102 (MAF Circuit Low Input)
P0335 (Crankshaft Pos Sensor A)
P0341 (Camshaft Pos Sensor A)

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Long version:

My knowledge of vehicles is lower-moderate. I am not afraid to get in there and repair issues myself, but almost everything I know comes from a problem happening, Google research, and a YouTube video. That being said, I have an issue that could be anything in my mind.

Driving home one day my vehicle started sputtering/wouldn't accelerate. I had to bring it to the shop instead of working on it myself because of work hours, and they reported the catalytic converter was melted through on the inside causing a clog.

The mechanic removed the cat and welded a straight pipe through it, I intend to get him to cut that out and put a new cat in it in a few weeks after I get paid and have the money to buy a new one. I just can't afford much right now and need a moving vehicle to get me back and forth to work until I can get the thing working at 100% again.

It ran smooth for about 30 minutes (just enough time for me to get home from the shop and for them to close, and on a Friday night with Memorial Day extending the weekend), and then it started doing what I described above. The idle is really rough, sometimes dying, I can usually start accelerating smoothly up to 3rd or 4th gear before it starts sputtering, and a few times in 3rd gear the battery hit 0 like the alternator stopped working (though the engine kept running). I thought maybe a fuel pressure/leak problem considering the cat was removed and now I smell fuel, but there's no fault code expressing anything like that, so maybe it's just the extra emissions I smell.

I can go out and replace one of the parts, like the MAF or the Crankshaft Pos Sensor, but I wanted to see if anyone had a better idea from experience. Like maybe the MAF is fine but theres a vacuum leak, or the Crankshaft code is wrong because now there's something wrong with the alternator. I work 12 and 16 hour shifts and my free time to work on this problem is limited, I don't want to spend time and effort listening to the fault codes if something else is causing them to throw.

(And I WILL get the cat replaced as soon as I can afford it)

 

UPDATE:

I went ahead and replaced both the MAF and the Crankshaft Position Sensor, and nothing. When I unplug the O2 sensors, it will idle fine. I can rev it up while it sits in neutral all day without any issues, I can even go in reverse without a bump or a noise. The moment I stick the thing into first, it dies almost immediately. A couple of times I was able to get it to start going, and made it around my block without it dying, but any time I went over 1500 RPMs, and every time I changed to a new gear, the engine will rock back and forth the moment I touch the accelerator. If I get it in gear and leave the accelerator alone, it will move without a bump, but touching the accelerator at all is a nightmare.

 

1st off, you dont tell us year make model. Second the the cat doesnt clog up or melt without a previous issue that need to be corrected

 

"Second the the cat doesnt clog up or melt without a previous issue that need to be corrected"

Yes, and I would think that at least 1 code should have been set when the cat "failed". Meanwhile, you can not expect it to run anywhere near right with the cat hacked out of the system. You might try disconnecting the post cat O2 sensor, but I think it would be best if you replace the cat before you drive it and/or throw any more parts at it.

Note: issues that can cause damage to the cat are often indicated by a rapidly flashing SES/Check engine light. Such issues often involve raw fuel being dumped into the cat due to ignition misfire conditions (fouled plug, bad plug wire, and/or bad ign. cap/rotor/dist). Fuel delivery problems can, of course, cause such issues (stuck injector, bad fuel pressure regulator, etc). Any of these issues might be why you're smelling fuel.

 

How about a melted or disconnected wire in the area of the cat converter. If nothing found then start with link below. If you want to work on your Blazer, get a capable scanner that reads live GM Enhanced PIDs, a digital multimeter, and a test light.

Android device and $30 will get you a decent scanner. I recommend either Car Gauge Pro (1998-2004 Blazers) or Dash Command (1996-2004 Blazers)and the BAFX Bluetooth OBD2 device as sold on Amazon. Car Gauge Pro is more difficult to use but does more (but not on 1996-97 Blazers - go figure). Dash Command does all years Blazers but charges extra for Enhanced PIDs, and you have to buy a set of enhanced PIDs ($10 extra) for each year. Torque Pro is good too, very cheap, and comes with GM Enhanced PIDs - but won't do cam sensor retard (common issue with Blazers). If you end up needing a fuel pressure gauge, just borrow one from your local auto parts store (with deposit).

Contrary to popular opinion, scanners and codes are not there to tell you what part to change or disconnect. They are only helpful when used in conjunction with a diagnostic procedure. Always deal with the lowest number code first, as other codes can be set by the lower code malfunction. P0102 is very low.
https://blazerforum.com/forum/diagno...plained-28157/

From your description, it seems you probably have an electrical malfunction of some sort that is causing all or most of your issues. Engine torques one way in drive and the other way in reverse, so I would suspect a shorted wire or something like that in drive but not in reverse. Also grounds can be a problem and there are MANY. Pay special attention to the three ground wires attached to the rear of the cylinder heads on the engine, and make sure the battery is securely grounded to the engine. Has someone had the engine out before?

p.s. unfortunately, by replacing the crank sensor you now require a crank sensor relearn in order to detect misfires correctly and only the most expensive scanners can help with that. Good thing the need to do this will not cause a misfire. You can have a relearn done (last thing in your repair) if the SES light comes on with a false misfire code. So don't be surprised to see a false P030x code in your future. Also don't be confused by some codes taking multiple failures on multiple key cycles to reset after clearing them. You can read about most if not all of them in the tech section of this site.

Finally, know that you should be able to get this vehicle to run and not miss without a catalytic converter - but you will have to replace it when other problem is fixed or it will set a code and turn on the SES light. It does a test and it knows if cat converter has been disabled or is not working.

 

Thank you for this information. I already have and use that very BAFX OBDII device with the Torque app.

There were no melted wires anywhere near where the cat was; everything is secured out of the way, it was one of the first things I checked. When I get home from work I will check the ground wires; the engine was removed about three years ago after a water leak caused a hydrolock. A re-manufactured engine was put in.

 

The post cat O2 sensor circuit will, most likely, cause problems with the cat missing. You are unfortunately in a 'catch-22' kind of deal with the cat out of the system. But then again, you run the risk of damaging the replacement cat if the issue(s) that ruined the last cat are not dealt with promptly.

As for the codes mentioned; were these codes set when you first began to have problems, or were they set after the cat was removed? As mentioned previously; the chances of having a cat meltdown without setting any codes is pretty low.

And Les Meyer's thoughts on welding caused damage are dead on. I've heard some bad stories regarding welding on feed-back vehicles. Arc, and even mig and tig welding can cause serious electronic issues. This is especially true if the battery was left connected during the process (these stories are mostly in regard to damaged sound and security systems). Anyway, my guess is that they gas welded the straight pipe in. But if they used arc, tig, or mig, then I'd speculate that is where your problems could have gone from bad to worse.

 

All of those codes were present during the initial issue, before the mechanic work. No new codes have popped up. I was able to drive the vehicle from the mechanic after the cat removal with 0 problems, no SES light, no bumps, and they test drove it a couple of times before I took it home. The moment I got home, about 30 minutes later, it started acting up again, and the same codes were thrown.

I am agreeing it's an electrical issue, but it's all the same issues before the cat was removed, before the welding job. I have to assume right now that there's just a short somewhere because it drove just fine all the way home.

 

Ok, that clears things up. I would, of course, start with re-checking the MAF, Crank and Cam Pos. wires and connectors.

I'd also check every under hood ground you can find. There should be a major ground located at the back of the pass. side cyl. head (2-4-6) with several wires held down with a 15mm bolt and star washer (IIRC). These gnd. wires are known for failing over time. I think there's another group of grounds on the driver's side of the int. man. Not sure about this tho.

Also be aware that the main eng. wiring harness is known for failing and/or shorting due to brittleness caused by heat and age (this harness is not cheap, so be extra careful).

Then there's the PCM ECM ECU (I forget which) ground that's known for causing issues. A search of this forum should turn up some good info on both the main harness and PCM grnd.

Meanwhile, other, more knowledgeable, forum members will likely be of more help than I've been...

 

One quick thing to do would be to look at the MAF reading with the scanner to see if it is in the normal range when the engine is acting up and go from there if an issue is uncovered.