Trick311

I have has this car for 4 years, the first year I got it, the catalytic converter had to be replaces, still under warranty so the dealership replaced it, about 6 months later it tripped again. Drove it for another 6 months and replaced it just before emissions testing. Tripped again later that year and replaced it with a high flow cat and this time did a 2 year registration. well its been tripped for about 6 months. Every shop keeps insisting to me that the O2 sensor is not the problem and I have been through 3 cats in just over 4 years.

99 Civic ex, runs great, any input on solving this issue would be great, thanks guys.

snake_eyes

its prob. running rich... if there is gas left over from combustion it will ignite in the cat causing the inside to crumble away or melt.

1.does it take a while to warm up? if you have a thermostat that is stuck open the car will run cooler than usual and the PCM (powertrain control module aka computer) will dump more fuel into the cylinders.

2.do you maybe have a leaking injector? a faulty injector can e dripping extra fuel into one of the cylinders

3. bad ECT (engine coolant temp. sensor)? once again PCM will think its cold and dump more gas in...

4.ignition timing? ignition timing can be too much advanced...

5.cam timing? have you had your timing belt replaced before this started happening? advanced exhaust cam timing will allow un burnt gas into the cat.


just somthings that popped in my head...

Trick311

Thanks for the reply, it actually warms up pretty quick, when running the AC while its warming up it idles funny but that another story.
Im thinking I may need to check the injectors and yes I had my timing Belt replaced about 6 months after purchasing the car, and actually im on my second engine as of March, blew the other one, d16's are cheap!

Im going to take it to the shop that did the engine swap and Ill let you know what they determine.

Former User

As mentioned, running rich is what typically kills the cat.

Any CEL codes besides P0420?

Have you recently replaced the spark plugs, wires, cap, and rotor and adjusted the ignition timing to spec? This is where you should start.

Trick311

Thanks for the input, Its been about 2 years on these spark plugs, going to check into adjusting the ignition timing, if its runnin rich which way do I want it to go?

Former User

Trick311

Thanks RonJ, Ill post results

Took it into the shop that swapped my engine, they checked timing ran some emissions test. They said it was running lean and strong, determined it was the cat that was bad.
The codes that were tripped; p0420, and bank 2 rich. so either cat or o2 sensor, shop recommended to replace cat.
Said it proly dumped **** down the pipe when the rods blew.
So any good after market cats recommendations? Running apexi wsII catback exhaust, stock exhaust headers with collector pipe mod