Failed smog twice, what could be wrong?? - Third Generation F-Body Message Boards

NC 91 Z28 · 10-23-2001, 03:04 PM

The first time my z28 filed both low speed and high speed tests.
High speed results: RPM 2730
Standard Current
HC 220 0011 Pass
CO 1.20 1.70 Fail
Low speed results:
Standard Current
HC 220 0092 Pass
CO 1.20 2.10 Fail
So I changed plugs, wires, O2 sensor, Cap and rotor, fuel filter, PCV valve, and HEI module and go for the retest.
Second smog test better but still failed, WTF!

High speed results: RPM 2504
Standard Current
HC 220 0009 Pass
CO 1.20 00.21 Pass
Low speed results:
Standard Current
HC 220 0074 Pass
CO 1.20 1.43 Fail
So I just barely failed on the low speed test, any one have any ideas or suggestions this is really starting to piss me off.

Could it be the 160 deg thermostat??

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Black 91 Z28, L98, 4L60, Dual cats, Posi.
Mods: Slp shift kit,B&m tranny cooler,B&m 3-4 upshift kit,Performance distributors HEI Dyna module,Msd 6a,Msd 8.5mm wires,k&n air cleaners,Home made air induction,Modyfied Mat,Hypertech power coil,Hypertech 176/166 fan switch,Flowmaster cat-back exhaust,dual dynomax super converters,160 thermostat,Tb bypass mod,Tb air foil, KYB's.
Red 79 Z28 with lots of mods.

OldBlue · 10-23-2001, 03:42 PM

nevermind I didnt read it well enough

[This message has been edited by OldBlue (edited October 23, 2001).]

MAXGTA2002 · 10-23-2001, 03:43 PM

could it be your converters? Thats the only thing left

do they have the honey cone or are the open all the way through? Just a guess.

Drakar · 10-23-2001, 03:44 PM

the 160 might hurt, you need to have a hot car as they were designed for emissions at like 190-210*, so make sure you drive around for awhile. Other then that Im not sure.

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1989 Trans Am GTA

NC 91 Z28 · 10-23-2001, 08:21 PM

I did pull acode 42 from the computer. Any more suggestions.

robert1 · 10-24-2001, 01:12 AM

CO is NORMALLY a rich mixture. If the engine senses it's cold, the 160,maybe it's adding fuel?

NC 91 Z28 · 10-24-2001, 01:44 AM

Thanks for the advice guys anyone else?

u r sofa king we tah did · 10-24-2001, 03:36 PM

try changing your ignition module if your getting a code 42. for the emissions, put in a 195 thermostat temporarily before you go to get your emissions done, and let your temp get up to around 210. that might make the difference.

NC 91 Z28 · 10-24-2001, 04:22 PM

I tried changing the ignition module but I still get code 42. My converters are only 2 years old could thet be clogged already? Thanks for the help guys any more Ideas,