Failed emissions.... Cats?
Le Mans Master
Joined: Dec 2000
Posts: 7,839
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From: San Diego, Ca
Of course it does and not that the Gospel according to GM isn't always right, but a High School Shop Class will tell you differently - not that it doesn't help the CAT, but if you understood Costs, you'd also know an OEM wouldn't waste the 10 Bucks per Check Valve if they weren't needed and they wouldn't be if it was designed solely as you think it was - the routing wouldn't be there at all - or when you enlighten the OEM's, please share some of the wealth with us.
Melting Slicks
Joined: Feb 2008
Posts: 3,286
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From: Palm Beach
Of course it does and not that the Gospel according to GM isn't always right, but a High School Shop Class will tell you differently - not that it doesn't help the CAT, but if you understood Costs, you'd also know an OEM wouldn't waste the 10 Bucks per Check Valve if they weren't needed and they wouldn't be if it was designed solely as you think it was - the routing wouldn't be there at all - or when you enlighten the OEM's, please share some of the wealth with us.
What has this got to do with warming up O2 sensors? I never said a word about your check valve theory. I challenged your statement that the air pump warms up the O2 sensors.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
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From: San Diego, Ca
Because O2's don't make voltage until about 600 degrees and that extra air provides an afterburner effect when the exhaust stream is ladened with HC's (rich mix to enable startup). None of this matters - the point was that a leaking check valve sucks in air that tricks the O2(s) into sensing a lean condition and the car will run rich. Our member resolved his problem with a scan, the best approach for an emissions failure. Of course I don't understand how that scan popped a 420 code unless it was a '96 or OB2 compliant, but if it fixed it, so be it. If it were mine, I'd retest and even it passes, snoop around a little if the CO wasn't 0 - which is how most leave the Factory. Getting that number lower leads to better economy, though most just care about passing.
Thread Starter
Team Owner
Joined: Apr 2001
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From: Overwhelmed as one would be, placed in my position.... DFW, TX
St. Jude Donor '05
Because O2's don't make voltage until about 600 degrees and that extra air provides an afterburner effect when the exhaust stream is ladened with HC's (rich mix to enable startup). None of this matters - the point was that a leaking check valve sucks in air that tricks the O2(s) into sensing a lean condition and the car will run rich. Our member resolved his problem with a scan, the best approach for an emissions failure. Of course I don't understand how that scan popped a 420 code unless it was a '96 or OB2 compliant, but if it fixed it, so be it. If it were mine, I'd retest and even it passes, snoop around a little if the CO wasn't 0 - which is how most leave the Factory. Getting that number lower leads to better economy, though most just care about passing.
Of course I don't understand how that scan popped a 420 code unless it was a '96 or OB2 compliant, but if it fixed it, so be it.
Last edited by Umrswimr; Apr 1, 2008 at 03:17 PM.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
'95 should be OBD 1 and wouldn't spit out the 420 (which is essentially a CAT failure). It may be that the Dealership has become too use to explaining things this way. I'd suspect that the majority of their work is warranty and anything with one is going to be OB2 compliant - so they might always note a CAT problem as a 420 something failure (there are 5 or 6 CAT codes). With an otherwise normal scan, your Vette should now pass.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
PS: Yes your Vette has Trouble Codes - just not that one or any that have anything do to with the CAT. OBD2 monitors the CAT through a system of O2 like devices in front of and behind it. To my knowledge, your '95 doesn't have that equipment. Had there been a problem with either System, there would be a Steady Check Engine Light until it went away (ie, self corrected - which is what your History Codes were all about - or someone fixed it).
