Hi
I just bought a used 1998 s-10 blazer 4x4 (to replace my 2000). I bought it Mon and drove for first time yesterday. It has a new used engine (which sounds and feels great) So I had been driving for a couple hours and started up a slight hill and it lost power I basically crawled up this small hill. It was strange I would push the gas and it may have got up to 10mph.
I parked it and called for a ride. After a 5 min wait I decided to see what it would do, so I started it and drove it to the house (4 miles) and it was fine. Took to the garage this AM and got a code saying the oxygen sensor was bad. They doubted that was the cause, they put on a new fuel filter. Drove fine for a couple hours then did it again. I parked hoping for the same result as yesterday but it would not be so. I proceeded to crawl back to my house and when almost there it started working again.
When i got home took the sensor off my 2000 (I has replaced it recently). I drove it for a little bit and seemed to have a little more giddy-up and it did not mess up. But as usual it never does it when someone else is watching...also I only drove for about 20 min.

Any ideas?
Thanks

 

That code could be important. What was it?

When this happened which best describes how you baby it?

1 Pumping gas pedal kept it alive

2 Flooring it made it die completely

3 Flooring it made it buck and jerk

4. Flooring it doesnt make it go any different, just no power

5 Barely push {feather} the accelerator to keep it going, idled fine

 

Kind of #4, it really makes no difference when you press the gas. The engine does not rev up it just inches along. It does not act like it even wants to die. Sometimes when I give it gas I hear a thumping noise coming from underneath, don't really sound like in the engine more in the center.
The mechanic did not tell me the code just said it shows the oxygen sensor.

 

It's the one between the cat and muffler, right?

Do you know how the exhaust sounds when it's healthy?

You have some indication of a clogged cat. Doesnt miss fire, buck or jerk, starts fine. Start using power , start losing power, cool off > okay.
When the cat is restricting the exhaust the individual exhaust beat fades and exhaust gets quieter.

 

The exhaust sounds fine, not loud or smoking. That is what I thought at first but my mechanic was not convinced. There a quick way to check? I was told if you could shake it that means it is bad/

 

Okay.. I dont think we're connecting. An exhaust with a clogged cat is not going to be loud and probably wont smoke.
A bad cat element might rattle when you tap on it with a rubber mallet. And it might not. Or it might already have fragmented and it's clogging the muffler.

If you've ever listened at the tailpipe of a healthy modern exhaust you can hear each cylinder's exhaust beat. If you know what it normally sounds like you can tell if it's not right. And putting your hand over it, fell each beat as a puff.. but It's like listening to a heart. if you never paid attention to how a healthy one sounds, then no one can describe it to you.

Yes, it is subjective.
The only easy test is to pull the O2 on the engine side of the cat and listen for too much exhaust back pressure. Again, it's subjective The will be loudness through the hole on a healthy system.. more on a clogged one. Problem being how do you do that while it's in fail mode

The only way I can think of to definitively tell is to drill a hole in front of the cat, thread in a nipple and hook tubing to a low range pressure gauge and watch what happens when it starts losing power. You could use the O2 bung, but I am not sure what effect that would have otherwise. One too many variables.

Indirect test: Hook a vacuum gauge to the intake and route tubing to cabin. Drive till it fails, If it's a clogged exhaust then manifold vacuum will drop {meaning move toward Zero} relative to rpm/ throttle angle.
Reason being: too much backpressure means there is still exhaust pressure in the cylinder when exhaust valve closes, which reduces cylinder draw, thus intake flow.
note it is STILL subjective and you have to pay attention to the vacuum v pedal depression and engine speed while it's running relatively well before you can see there's a change.

Please note that this test works best when symptom is loss of power while otherwise no missfire, bucking or jerking.