Stalling problem, threw P0420 code., help?!
 

Hi,

First post here. I've got a 99 Civic EX that's developed a stalling problem. I can start the car, drive it a bit, and stall it intermittantly while it's driving or the stalling can occur when in idle... but usually always when the engine is warmed. When the car stalls, I can crank it (which it does crank), it's pretty even money that I won't get an immdediate start-up.

I had a similar problem a year ago, changed the ECM, which didn't resolve the problem and took it to the dealership... they replaced the ignition switch, based on a recall, and it ran fine until now.

Check engine light was on, solid, and I checked the single code that wsa initiall thrown... P0420. I erased the code and drove it again, it stalled while driving low speed through the neighborhood, and no code has been thrown, but the battery light came on as I tried to crank it over.

The outside temp is not hot, and the stall happens after the engine is running; I can get it to start nearly always after it's been sitting for a while.

Q: Given the code that was thrown... any thoughts on what could be causing the stalling aside from a bad catalytic converter or O2 sensors?

Also, I had read on another post that an alternator problem could cause a stalling situation. I took a meter to the battery posts when the car was idling and it mostly showed the battery was getting charged at 14v, but would also intermittently show a drop in the voltage for a fraction of a second... sometimes down to 4... sometimes to 2. This would happen every few (about 10 secs...). Does this sound normal?

Thanks for any advise and/or help... ~ rob

Re: Stalling problem, threw P0420 code., help?!
 

battery voltage should not drop below 12 at any time. maybe you were just not getting a stable connection with your meter. just make sure the alternator power cable is tight and also the battery clamps.

P0420 Catalyst System Efficiency Below Threshold (Bank 1)

This means your catalytic converter is dead and probably clogged too, causing the engine to choke and die.

Re: Stalling problem, threw P0420 code., help?!
 

How can I check for a bad converter and can they be cleaned out?

Re: Stalling problem, threw P0420 code., help?!
 

well theres nothing you can do to really check, aside from taking it off but then your exhaust is gonna be very loud. its possible to clean it but then it wont work at all to reduce pollution. its a metal piece with a honeycomb mesh inside and that is what has all the catalyst that makes your car run clean. it can also clog up over time.

Re: Stalling problem, threw P0420 code., help?!
 

I've taken my converter off. Looking through it, is there a difference between a good an bad converter?

Re: Stalling problem, threw P0420 code., help?!
 

you wont be able to tell by looking. i guess you can drive the car without the converter to see if the problem goes away, but its gonna be really loud and smelly.

Re: Stalling problem, threw P0420 code., help?!
 

Well, just shaking it knocks peices out of the O2 sensor hole... can I be fairly certain that it's plugged or out of service. Also... there's a screen that seems to be on the tip of the O2 sensor that's melted into the tip of the sensor... another problem?

Re: Stalling problem, threw P0420 code., help?!
 

yeah if chunks are coming out, its done. if you really feel like messing with it, knock out all the mesh inside til its a clear pipe and reinstall it. if the car runs fine, you know why. the 02 sensor in the cat does not affect how the car runs, so even if a chunk of cat fell on it and burned in, that wont affect anything except throw the engine light on. post a pic of the sensor and i can tell you for sure.

Re: Stalling problem, threw P0420 code., help?!
 

Tested the Cat sensor and although it was operational, it worked just out of spec, so both sensors are going. Waiting for parts, we'll see how it goes...