I have owned a 91 civic for a year or so. Replaced the CC and muffler last August. It had been bogging down after running for awhile. Fast forward a year and I am now experiencing the same thing. I am not a huge gearhead, but know my way around mechanical things, so bear with my ignorance.

I had the engine tuned last year with new plugs, wires, dist, etc.. along with the timing set. I thought I had the problem solved. Then last month all the symptoms returned. I replaced the cat again, and the O2 sensor thinking maybe a bad sensor, though not getting any CELs at all.

The guy who installed the Cat was a random muffler guy around town who just "eyeballed" what he thought might work on my car size wise. Would a model specific cat work differently?

The car starts and runs fine, no stumble, OK gas mileage, no smoke at all from the tailpipe. I pulled the plugs and they are on the white side. I will post pics tomorrow.

Any thoughts on what could be going on?

Vaccuum leak?
Head gasket?
Old worn out motor?

HELP!

 

Do you have to have the CC?? I know a good way to fix the problem if you don't

 

Maybe some other Seattle folks can chime in on that one? I have no idea. If that's the case, i'll be under the car tomorrow.

 

Do you have to have the car smogged? Emission tested?

 

Yes. That means CC I believe. At least for another 4 years or so until the age of 25. Then we are exempt.

 

Ah, well from what I know, being too rich or too lean can destroy a cc, not sure how fast, but white plugs mean a lean condition afaik, so you may be running too lean.

 

There's generally one reason for a cat to go bad -- the engine is running rich. Unburnt fuel in the exhaust burns in the cat and melts the substrate. Before you install another cat, fix the rich problem, which can have many different causes, including ignition system misfire, exhaust leak, high fuel pressure, stuck open injector, bad FPR, etc.

 

White/light grey/light tan plugs are actually good.
Yellow would be lean... unless you are talking flakey white stuff all over it.
http://www.ngksparkplugs.com/tech_su...qs/faqread.asp

Did you go with a really cheap cat? It could have been poor quality and just isn't lighting up anymore.
You can drive the car around a bit and take it to a muffler shop. They can put it up on the lift and use a laser thermometer to check the inlet and outlet temps on the cat to see if it's lighting up.

BTW: some sensors won't throw a code when they are on their way out. O2 sensor sometimes gets "lazy". It will send ECU just enough to not throw a code, but not correct to run the engine properly. You would see the rich/lean condition on your plugs though.

 

Updated OP with plug pics.

 

The plugs don't show a rich condition, but running lean won't kill cats.

 

What next then?

 

Ok, looks like the head gasket and oil pan gaskets were the culprit. I never noticed oil on the driveway at all, but I must have been because the oil level was almost bone dry. No noticeable oil from the tailpipe EVER.

If I have to dig that deep, is it worth swapping heads with another model?