ffspiel

Hello People of HT,

First off, thanks for being available to answer questions... a much appreciated service you people provide free of charge.

Problem: I own a 99 Civic EX, 4 cyl., auto that has developed a stalling problem. The car starts and idles fine, has 166k miles on original engine.

When driving, it might stall at any speed, and I can sometimes restart the engine. Engine will always crank, but restart is questionable and pretty intermittant. When it stalls, it usually does so when the engine is warm, although outside temp might be cool/warm or whatever.

There is a solid, amber, check engine light on and it threw the code P0420, pertaining to a possible catalytic converter issue. I erased the code and have since stalled it, but no engine light or thrown code has come on. Upon stalling and attempting to restart, I noted the "battery" dash light linger for a second or two... no restart; able to crank, lights on, no dimming. This morning, started like a champ... no idle problem.

Also... this problem, or a similar one, occured about a year ago. I ended up replacing a ICM (I believe... don't remember) which didn't resolve problem. I then read up on a recall for the ignition switch, which was replaced by dealer, resolving that problem.

I have read that due to this particular code being thrown, it is nearly always a bad cat, not being a tech or having advanced diagnositic equip or experience, I just don't know, but my gut feeling is that this problem is electrical (I know this sounds vague, but again, I'm not sure...).

Q: any chance it threw this code as the vehicle was stalling due to a condition that developed when something else was crumping (like an electrical problem... ignition... coil... main relay...), and not a cat problem?

Q: Can CAT's be checked or cleaned?

Q: If indeed it's the CAT, any good online sources for an OEM parts?

Q: How can I proceed to diagnose what I can at home?

Any help or alternate thoughts on what could be going on would be very appreciated....

Best Regards,

Rob

ffspiel

I'l post this to myself and anyone who has experienced similarly described problem. (Disclaimer... I'm NO mechanic, I've just been informed and have informed myself about MY particular problem, and will shortly do the work to resolve it. Not sure if this will correct the above mentioned issues, but I hope so...).

From what I've gathered thus far, there is a high likelyhood that my catalytic converter is toast, along with possible upstream O2 sensor being bad, thus affecting the air/fuel mixture to cause an early demise of my catalytic converter. Findings thus far:

Of the two O2 sensors, one is certainly bad, the one on the cat; the other O2 sensor )upsteam of the cat) has yet to be removed, but I'm replacing it anyhow and will test it once I've removed it. I'll post results here.

The old cat was removed. There seem to be at least three honycomb walls in the cat. The honeycomb is a grid of squares about .5mm or less in size and about an inch thick each. The honeycomb on the upstream and downstream side is visible once you've removed the cat for observation and should (both.. at least) be intact.

Looking through my old one, I can hold it up to the sun and see a diffused view of sunlight coming in; it's (the view of the light) is about dime sized. The old cat has got cracked and missing material from the upstream side, broken material on the inside, but a fairly intact honeycomb in the rear. I've been told this defect makes it bad now.

I'll be replacing the cat (don't forget to order a new gasket for it when you do your replacement. I'll also be replacing both O2 sensors, because the first was bad and I'm already down there... may as well.

As stated, I'll repost the results of my repairs letting you know if this took care of the problem.