2000 Acura Integra Catalytst CEL code, Custom parts

Tiny
KISIL
  • MEMBER
  • 2000 ACURA INTEGRA
  • 4 CYL
  • FWD
  • MANUAL
  • 76,000 MILES
My Integra was giving me CEL codes for a bad front O2 sensor and "catalyst low efficiency." I had the cat replaced, but the guy who did it

left the old sensors, so the O2 sensor code was still there. I drove about 500 miles, then replaced the O2 sensor with a Bosch & reset the

computer. The CEL came back on, with the cat low efficiency code again. The new cat's OEM, and I have low to medium confidence in the guy

who installed it (long story).

To complicate things, the car has exhaust headers and an after-market air intake with a sketchy foam vent (which I'm planning to replace

but haven't yet - could that affect my emissions?) It also has california emissions - I'm unclear on whether that affects the ODBII, or if

it's just a certification. The few mechanics I've talked to want to put a manifold back in, which seems dumb to me, as I get 4-8 mpg

better than CAFE ratings. You'd think I'd be able to get the computer to like the aftermarket parts. That said, I still need to fix this

so I can pass emissions, so ultimately I'll go to stock if I need to.

I'm wondering whether I could have poisoned my new cat by using the old bad sensor (& therefore running too lean) for so long. Someone

also told me that the cats could have been poisoned by the extra heat from having the headers instead of a manifold - that the exhaust

doesn't cool enough since it gets out to the cat faster. That story seems unlikely, since the difference really isn't that big.

I've also read that this could be a mass airflow sensor problem, but I don't understand how that works.

So the options I've thought of are:
- replace just the cat
- replace the cat & both sensors
- go back to a stock manifold & replace the cat & both sensors
- replace the mass airflow sensor
- fix the intake


I want to spend as little money on this as I can, but I want to make the fix permanent. That also means I'd rather buy OEM parts (vs.

paying the dealer markup), but I can't swap the cat out myself, as it's welded in.

What do you think the most likely problem is, and what's the best bet for fixing it? Is there anything I haven't thought of here?
Friday, February 8th, 2008 AT 5:49 PM

3 Replies

Tiny
MASTERTECHTIM
  • MECHANIC
  • 4,750 POSTS
Well first you can look at the front and rear o2 sensors with a scanner and find out if you have a bad converter. My opinion is if you still have cat low efficiency problem than you probably have a bad cat converter. The intake and exhaust should not effect the converter. If the voltage on the o2 in front of the converter is varying up and down, thats good. The rear o2 voltage should stay relatively the same, if it fluctuates like the front one then your cat is no good. **It happens** hope this helps
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Friday, February 8th, 2008 AT 5:54 PM
Tiny
KISIL
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Thanks for the quick reply. Is there any chance that the headers are responsible for the poisoning?
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Friday, February 8th, 2008 AT 6:43 PM
Tiny
MASTERTECHTIM
  • MECHANIC
  • 4,750 POSTS
Not a chance
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Friday, February 8th, 2008 AT 6:46 PM

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