I took my '91 Z28 to get my emissions tested and it failed. Recently I put a new catalytic converter on and the car is completely tuned up. After it failed for the first time, I replaced the O2 sensor and ran some fuel injector cleaner through it. I took it back and it failed again the same way. The only test that it fails is the CO % but it passes all the other tests with ease. The allowable for CO % for my car is .69 and I got .97 and 1.04. Someone help me out here and give me some suggestions. By the way, the Air Injection Reaction is completely removed and I have Hooker shorty headers. Maybe that's the problem but is there any way around it?

Thanks

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1991 Z28 - 350 TPI, T56, McLeod street clutch, ported plenum & runners, AFPR, Holley Annihilator ignition box and wires, Hooker shorty headers w/o AIR, no cats, Flowmaster muffler, homeade ram-air, SSM subframe connectors, Steve Spohn adjustable torque arm and T56 crossmember

 

CO is the not so "good" chemical reaction of burning carbon and oxygen together. The problem is that there isn't enough oxygen left afterward. As CO is a polutant, CO2 is the "good" chemical raction of the two. You need to hook up your AIR pump to get enough CO2. That will help burn off HC as well as add O2 to CO and that produces CO2.


Or so I've heard.

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'82 Firebird, dead stock, 9 bolt disc rear, over 200,000 miles and still going strong, more to come...

 

OK, that's what I was afraid of. Is there any other way to get by this??? Maybe disconnecting a vaccuum line??

Thanks

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1991 Z28 - 350 TPI, T56, McLeod street clutch, ported plenum & runners, AFPR, Holley Annihilator ignition box and wires, Hooker shorty headers w/o AIR, no cats, Flowmaster muffler, homeade ram-air, SSM subframe connectors, Steve Spohn adjustable torque arm and T56 crossmember

 

Its a guess, but maybe dropping the fuel pressure a bit could do the trick

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92 Camaro RS LO3, 5-spd, T-tops
Performance:
SLP 1 3/4" Headers (Coated by Paul Barry Motorsports), Flowmaster Catback Exhaust, Fastchip Performance PROM, Centerforce Dual Friction Clutch, Xact 8mm wires, Open Air Element w/K&N Filter, Z28 Grille w/aftmkt fog lamps
Electronics:
Alpine 8030 Alarm System, Valentine One Radar Detector (How did I ever drive without one?), Pioneer DEH 7450 Head Unit w/6-pack CD changer, Pioneer DEQ 7600 Sound Processor, 2 Kenwood KAC-846 Amps powering 2 12" Pro Red subs, 2 Pioneer 6x9 and 2 MTX 4x6 speakers.
NEXT UP: TBI mods, Edelbrock performer intake

 

Usually if you remove a vac. line it will cause another cylinder to fire poorly or cause a small miss.

This will most likely cause the HC to go through the roof. Not what you are looking for.

I would go with Pukka's suggestion and try dropping the fuel pressure a little.

Do you have a chip??

What is the engine temp when running the test??

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ASE Mechanic/Machinist/Smog Tech

1999 NBM Trans Am
1986 Chevy 3/4 ton pick up
1981 corvette
1995 Kawi ZX6R

GO #3

[This message has been edited by Engineboy (edited January 09, 2001).]

 

Nope, no chip. Also, the car was practically overheated by the time the test was over.

 

heres a little trick buy a crappy O2 sensor and strip the wire a little and tape the "open" wire to the frame and then plug it in. I do this all the time when i go for emissions i have no AIR eather passes with ease only do this when testing cause you get an EXTREAMLY Low O2 reading like only 12 yes only 12 nomals is 300-800-500-400-800 the car will surge and idle like **** but it'll pass it'll run VERY Lean

 

retard the timing

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Rick
90 Camaro RS 305 TBI
400 small block, Hooker 1 3/4 LTs, Random Tech Cat, Hooker aero chamber cat back on the way!!
TH700-R4 with Trans-Go shift kit (corvette servo here...but not installed yet)
MacEwen Motorsports White Gauge Overlays
14" K&N X-Stream Open Element
GTS Headlight and Taillight covers
5% Limo Tint all around
Classic White Chevy Bowtie sticker on rear window
http://www.geocities.com/esvalenz

Man if my camaro were a rice-rocket all those mods would give me what...easily 50-60 hp!!!

"Just because I've done it, doesn't mean I knew what I was doing!" - Me

 

Hmmm...interesting. So unhooking the O2 sensor won't effect any of the other tests in a negative way?? Has anyone ever done this? Here in Atlanta, we have to do the dyno test as well as the tailpipe test.

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1991 Z28 - 350 TPI, T56, McLeod street clutch, ported plenum & runners, AFPR, Holley Annihilator ignition box and wires, Hooker shorty headers w/o AIR, no cats, Flowmaster muffler, homeade ram-air, SSM subframe connectors, Steve Spohn adjustable torque arm and T56 crossmember

 

I dont have my sheet but it passed we too have the tailpipe thing on the dyno. i hate those bastards driving my car

 

your not unhooking it your just exposing the wire and grounding it out. If you unplug your O2 your reading will be about 350-400 but grounding it messes it up and lowers it making the car surge for gas

 

The grounding method makes NO sense at all. A reading that low will make the ECM pulse your injectors MORE to give it MORE gas to compensate for the overly lean condition the 02 is seeing. Remember 800-900 to 1V is what causes the ECM to think it's running very ruch therfore cutting back on gas, NOT when it reads 12mV.

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92 Z28 L98 350
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Ported stock heads, XR270HR-10 cam, TES headers, Crane AFPR, Flowmaster catback, MSD ignition components.
Best ET 13.5@105 mph
"Take that auto, drop it in first, hold the brakes, stomp the gas and grin from ear to ear! :-)
Click here to see my car at Truspeed.org

Check out TruSpeed at http://www.truspeed.org
Check out the Bin Archive at http://www.truspeed.org/bins.html

 

This may be a desparate measure to partly replace the smog pump function, but here goes:

Does this new cat conv. have a nipple connection for the smog pump? Go to a junkyard and get one of those AIR system check valves and bolt it on to the nipple.

The exhaust system contains pulses of high and low pressure. What you want to happen is for that check valve to open during the low pressure part of the pulse. Both F*rd and GM used that principle during the late 70's and early 80's on some models. That little bit of extra air coming into the cat may do the trick.

[This message has been edited by jrr (edited January 10, 2001).]

 

No the new cat doesn't have the tube coming out of it. I was considering doing something like this except making the valve right before the converter. Do you think this will still work?

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1991 Z28 - 350 TPI, T56, McLeod street clutch, ported plenum & runners, AFPR, Holley Annihilator ignition box and wires, Hooker shorty headers w/o AIR, no cats, Flowmaster muffler, homeade ram-air, SSM subframe connectors, Steve Spohn adjustable torque arm and T56 crossmember

 

A friend at work mention to me one time that to warm your engine really well before you go to get it tested. Supposedly he passed much easier and faster than taking the car in somewhat cold.

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Shouldn't bother putting this but hey what the heck:
1988 Maui Blue Firebird 305 TBI stock (w/ 190,000+ miles and still running strong )

 

Also, fill up with 87 octane gas. Lower octane burns more completely. And change the oil, and check the PCV system for clogs.

 

Ive heard the opposite, I thought that the higher octane gas burns off more completely?

 

Mikos1980,
just curious, but wouldn't your method cause the NOx to go up dramatically? -justin

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Justin 87 GTA--organizer: "NY2K" Gathering. Blk/Gld w/Superam, 355cid Trickflows, forged pistons 9.5:1. Auto 2,600 stall, 3.45 9 bolt disc, Best time & mph 13.567 @ 101.900 w/ a poor 60ft. Best mph: 104.3 *This car is 100% NYS emissions legal, w/ all emissions controls!* "If you want to have a fast car, hang out w/ those who do!"
http:// www.community.webtv.net/munks87/JustinsGTApage.com