After replacing all mount I got a P0401 code and the car now feels rough. Has anyone have any idea what could be the issue? I clean out the EGR valve, TB, IAC and MAF.

 

Did you connect your o2 sensors? That code can be a whole domino effect of problems, but it says that your cat is inefficient. A faulty or not connected o2 can do it.

 

or if lets say you change the o2 thats on the header and still throws it, then you can likely kiss that header goodbye and buy a ~$500 part to correct the issue like i did... depending on where you live, like in CA or NY, it has to be 50 state legal and will cost ya. i was lucky to find my header for under 500 on amazon thats legal...

but before you go blow out cash, check the connections and reset the ecu and/or replace that front o2 ( $60 or so )

 

yeah I get that, but just changing out his motor mounts wouldn't have made his cat go bad...... I think something is unplugged somewhere, or he tore a wire somewhere


and you can find a 50 state legal header cheaper than $500..... $410.79 from rock auto

 

That code says its for the EGR. Check the vacuum lines to the EGR first. If they look good you may need to pull the EGR and clean it. Be sure to get a new gasket first. Be sure to pull your battery cable as well to reset your fuel trims.

 

I replace the cat, and I did clean out the EGR but i did not replace the gasket.....all lines are on and I don't recall moving anything around there.

 

Oops my bad, I was thinking p0420 - that is the cat code.

So before you removed it and cleaned it, there were no codes and it worked fine?

 

The Code showed up after I replaced all the motor mounts, however, I did clean out the EGR valve as soon as i knew what the code was to see if that would make the code go away

 

Again changing your mounts didn't trigger the code. You wither yanked on, broke, or disconnected something. If you cleaned your egr and reset the computer and it came back, and you have verified your wiring is ok, then replace the egr