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92 400e catalytic converter wuestion
- Thread starter Rosenfe
- Start date
How exactly is you cat "bad"? Has the honeycomb broken internally and it's rattling?
Absolutely NOT.
... back to question #1. Be careful of emission test shops that are quick to interpret a smog failure as "bad cats".
Not diagnosed by a shop. Rattling drivers side cat area , exhaust smell , engine runs rough. Distributor caps are good- just checked. No warning light
OK - if it's rattling, that's bad.
Sounds like classic symptoms of a misfire that caused raw fuel to be dumped into the exhaust, which killed the catalysts. Bummer.
The caps may look fine but you're still almost certainly dealing with a misfire. Do your caps have the additional vent slots as discussed here?
There is almost never any warning light from a misfire... almost never any fault codes either.
Yes I cut extra slots. I think misfire happen a while ago. That’s when I put new caps rotors and checked insulators.
Have you had the msifire / rough running since cutting the extra slots?
Trying to figure out if the catalyst damage was caused by long-ago misfires, or if there is a current / recent problem.
With a rattling cat (broken honeycomb) it may not pass CA smog.
It’s been running well, only in the last few weeks a momentary roughness on startup- possibly from cat going bad
A misfire can cause bad catalysts... however, bad cats won't cause a misfire nor momentary roughness on startup.
About the only problem from bad cats will be reduced power, if the cats are blocked enough to prevent normal exhaust flow... oh, and a failed emissions test. That's it.
Edit: Badly plugged catalysts can also cause problems under load at higher RPM's, as described in the next post.
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This is an extreme condition I had but when my cats were clogged from a rear-end accident and I was holding it in second gear to troubleshoot why I couldn’t get the engine past 4000 RPM, I had a few massive misfires/backfires—enough to cause a head gasket leak. But I understand you are referring to normal driving.
