Replace catalytic converter???

[phrodgers]

About a year ago I was having problems with my catalytic converter and had to replace it. My check engine light came on but didn’t think anything about it because the car still ran fine. Last week having inspection due I replace the O2 sensors to try to get the light off. Now I have some problems.
Just in the morning and after the car has been sitting awhile it starts out fine but around 30 to 40 mph I lose all power. My rpm don’t drop but it just doesn’t want to go. After that it runs fine for the rest of the trip.
I was going to replace the converter again thinking that is the problem but is there any ideas what else it could be?

 

[JDM melbatoast]

have your codes scanned by autozone or if you have an obd scanner that would help also. trying to pin point the problem will be 10 times easier once you know those codes... your problem sounds electrical so your code will be like PXXXX let us know the code/s

 

[phrodgers]

I got it scanned and got code p0420.

 

[Solid_Snake]

P0420

Catalyst System Efficiency Below Threshold

Yup its your cat.

 

[phrodgers]

But why am i losing power now after replacing the O2 sensors?

 

[Billy.]

you only needed to replace the downstream o2 sensor, which actually has no effect on the performance of your engine. its for emissions monitoring ONLY. if your cat or o2 sensor goes bad you will get the Catalyst Efficiency Below Threshold code. if you replaced your upstream o2 sensor, you may have installed it incorrectly which has your computer all out of wack

 

[Jersey8]

since it appears you replaced both o2 sensors, you need to replace your cat if your still throwing the p0420. your cat may be shot, and clogged up, which will cause it to restrict exhaust flow and cause your engine to lack in power.

 

[Genuine Rolla]

^^

Could be that. When I had that problem, I just did the spark plug non-fouler trick for the 2nd o2 sensor and the CEL light for it has been off ever since.

 

[dxhepa]

Check your car for vacuum leaks, and check if all of the rotors on the crankshaft rotate freely.
All those have similar symptoms.
On my 98 civic I had the same problem and it ended up being the AC compressor.
You might be replacing parts that are perfectly good if you don't check for these.

 

[Mad-Mike]

I got an easy question, when you take the cat off your car and put it back on, do you need to replace the gaskets or can you reuse them again?