Does anyone have a idea what could be cause no acceleration and a loud humming sorta noise coming from the engine when I accelerate. There was a exhaust leak but it’s still making that noise and doesn’t really have power. I only have a code for PO155 (O2 Sensor Heater Circuit Bank 2 sensor) the vacuum leaks were also fixed but there still a loud humming noise when trying to accelerate and it’s doesn’t move anywhere. Doesn’t really wanna shift either. Really can’t go over 80 because it’s no power. Can anyone help!?😭

 

Sounds like your fuel pump could be on its last leg, something along those lines. If you were in limp mode or had something serious enough to cause this symptom it would almost certainly generate a bunch of codes. Did u do the repairs and then found this problem on the first drive after? Or was anything done at the time this became a problem?

 

I had something similar, I had debris from my cats all in my exhaust. No power. Changed the cats and had the debris removed from exhaust system. I also had the 02 sensor code when this started. O2 sensor was fine. Still wish I would have put the Tanabe exhaust on at that time. Now I have a OEM heatshield rattle.

 

I have seen a catalytic converter disintegrate internally, so the honeycomb was a bunch of big chunks that wouldn’t allow much airflow thru the converter. It was pretty easy to diagnose by simply giving the converter a a good hard slap, and u can hear the pieces flip around. This would also create the described symptoms. I don’t recall the humming noise that is being described. But it’s clearly got some type of basic elemental problem, air flowing obstruction between the air filter and exhaust tip, or a lack of fuel pressure. If it was a spark issue u would almost certainly get a CEL. It would help if I knew the details of the onset of problem? Was the car running great and then just all of a sudden this happened? Or had it been stored and then acted this way once it was fired up for the first time? Or was there some repairs done by the owner and it’s benlen acting like this ever since?

 

before the repairs it was making a loud blowing noise from underneath with slow acceleration and very loud but after its now blowing from under anymore but it’s not going over 25mph. Just kinda revving up now

 

it started acting funny and the codes that came on were random cylinder misfire, and then misfire in 1,2 and 3. Replaced all of the plugs and the coils but still was misfiring and driving bad. Checked the wires and some were pretty corroded so dealt with that and now no misfiring but after that seems like it picked up a few exhaust leaks. Was driving a lil better but not like how before the misfiring had started. So fixed the leaks but now there no power at all. Literally really can’t go over 25mph

 

The leaks would give a form of pressure release for the exhaust to escape out of, which would mean there is less back pressure in the exhaust to cause loss of power. Probably when you patched the leaks you sealed the alternative pressure exits, meaning that the exhaust is now under incredible pressure and that the back pressure is quite high now. Like the others said, it is most likely tat a catalytic converter disintegrated internally and now webbing is stuck in the pipe. You'll hear when there is a blockage large enough, too. Picture gasses exiting the exhaust ports at over 120ish mph then slamming into a wall of catalytic converter webbing. Even though it's inside the pipe, you'll still hear it. At this point it can't be related to spark, and if it is bogged down that is not an O2 sensor. A bad O2 sensor will provide false information which will hinder performance but it will now kill power like this.

 

Your O2 code is from the downstream sensor, indicating there is something wrong with the converter. And a clogged converter would produce all of the symptoms u have described. It could be clogged because of contamination of some kind or because of internal disintegration. Does your car have multiple converters? I would assume it has at least 2 based on the code, and that would also fit with the misfire from half the cylinders. It shouldn’t be difficult to determine for sure if you could look into it, unfortunately I think that means removing the entire exhaust manifold. Try giving it a few smacks to the converter and listening for anything loose internally. That would confirm that it’s disintegrated, maybe a laser thermostat (touch-less thermostat that u point at the target and pull the trigger) would help in diagnosing if it’s plugged with some contamination. I would think it gets substantially hotter normal if it’s not flowing correctly.

 

I just remembered another way to help diagnose your vehicles issue. If u pull the front O2 sensor out and then fire it up, if it has a noticeable amount of air blowing out the bung, your converter is likely not flowing correctly. They make a gauge to specifically check this, and you can check the pressure fore and aft the CC. If it’s flowing correctly you should have minimal pressure, like around 1 psi and the higher it is, the more likely it’s your problem. I am guessing these exhaust leaks you have been experiencing recently are another symptom of a plugged CC.
You could replace your exhaust manifold with a header and then install a high flow cat or even a test pipe or something depending on the emission laws in your area. It’s a federal law to remove the CC, so to remain in full compliance that’s required in a state like California you’ll want to track down either a used one through a wrecking yard. The other option is to find a new replacement, eBay has aftermarket options starting just under $500. So you’ll need to figure out what fits your budget. It is something that has quite a bit of info in the DIY section here on CL, if you want to tackle the job yourself and save some money, or almost any repair or exhaust shop can take care of the labor, just source the replacement before hand and you’ll save some money and choose the replacement yourself.

 

I got my cats OE direct fit for 399 from Rock Auto. Midas then removed my 3rd cat and straight piped that. I am good to go now!