My check engine started coming on in my 98 honda civic,4 cylinder,,,with 270 km on it,,the car is running really rough,you halfto really step on the gas to get it going,,then the engine light starts flashing after a bit!!!!! i got it put on a computer at a shop,and the guy said it showing 02 sensers,and catalact converter,,,which might i try first? does anybody know thanks for the help

Stratmando

Personally, I would change the Oxygen sensors first, clear codes then try again.

this8384

Which codes are stored? Find out and post them here.

shazamataz

Surefire sign that your cat is gone is a distict ticking noise coming from under the car, especially when you down gear...

Stratmando

I don't have the excess Money to pay for a Catalytic Convertor, and getting both codes, I would Do the easiest/cheapest/fastest first.
O2's are cheaper than convertors, TXgreasemonkey on this site will have good input, or may be on his troubleshooting Hondas. Back in a second, will get link.

this8384

I'd hold off on replacing anything until you're absolutely sure what the problem is. Something as simple as a pre-O2 sensor exhaust leak can cause both the sensors and the convertor to be reading wrong.

Again, get the exact code numbers and post them here. That way we can give you the best help.

Stratmando

Another thought is to use a vacuum guage as you would to determine clogged exhaust.

this8384

Yep - a back-pressure test will let you know if the convertor is flowing efficiently or not.