I have a 2001 Jimmy, rough idle, can't get the RPMs above 1500 without it stalling.
People have said try the fuel pressure regulator, tested fine, replaced anyway.
People said fuel pump, tested fine.
People said fuel injectors, pulled, had them bench tested, tested fine, replaced with upgraded harness I already had planned on putting on.
People said cat, well can't get it to idle steady or the RPMs high enough to compare the upstream and downstream sensors on scope, so I pulled the oxygen sensors and ran it without, yeah the computer was trying to compensate for no input, but it was actually running good and didn't stall out at 1500 rpm, had full throttle range; replaced all three oxygen sensors and with the sensors in it's back to running like ****.

Could it still be the cats?

If I had any hair left I would be pulling it out.

PLEASE HELP!!!!!

 

So you physically removed the O2 sensors from the exhaust and it ran better? From what little I know, that would point to the cat maybe being plugged which will choke the engine with backpressure from the exhaust not being able to flow. If your cat is obstructed, removing the O2 sensors would allow the exhaust pressure to escape through the O2 sensor hole, bypassing the blocked cat.

Replacing the cat will only be a short term fix. You need to address what caused the fouling in the first place, which I believe is the engine running too rich.

Hopefully someone who knows more about it than me can chime in with some helpful advice.

 

Yes this points to the cat. El Beutor got it almost all right. Leave the O2 sensors in and unplug them and see what happens. Final check, put a back pressure gauge in a single removed O2 sensor and measure pressure. EB is also right that the offending condition must be corrected or you will kill the new cat (if confirmed). That can be rich fuel but also coolant, oil, sealants.

George

 

Yeah, not O2 sensors ran fine, new sensors runs like garbage.
I'll drop the cat this weekend see how it runs and probably order a new cat.
Hopefully since I just replaced the spider with an updated one that will take care of it running rich, it started acting up right before yearly tune-up and smog check, so I'll put the new wires, cap and rotor on that I have sitting here too.

Thank you.

 

I am trying to separate the reason why it ran better. Is it because the O2 sensors were out of the their mounting points relieving back pressure and/or because they were disconnected from the wiring.

George

 

Unplugged the sensors, still garbage.
I don't have a back pressure gauge, so I'll drop the cat this weekend see how it runs and probably order a new cat.

 

OK then you most likely have a plugged cat. Let us know how it turns out.

George

 

I'm going with because they were out.
leaving the new O2 sensors in but unplugged, it still runs like garbage

 

I'll help!

Here, these should help.

 

BlueRidgeMark, if you're not going to be helpful, at least don't be a jerk that's not what this group is about.