I sure could use some help here. I've got an 83 Z-28 with a 305 and a 4 barrel. I'm having a hard time getting it to pass the CT emmissions test. CO seems to be a little too high. I've replaced the plugs, air filter and done a general tune up. The check engine light would come on every once in a while indicating the TPS out of adjustment. Couldn't get it to go off completely,, so I ended up buying a rebuilt carb. It seems to be off completely now. The cat is only about 2 years old. I'm kinda at a loss at what to try next. Anybody have any suggestions? The NO level is fine but the CO level is just a little more than the allowed max.

Thanks a lot,
Matt

 

Welcome aboard,
Here is a trick I've heard, first get your car down to about 1/4 tank and pour in a bottle of rubbing alcohol and drive around for about 20 mins. before the test, this allows the engine to clean itself out a little.

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'86 IROC
T-TOPS, TINTED WINDOWS, BRAKE LIGHT BLACKOUTS
GM GOODWRENCH 350
EDELBROCK TES HEADERS
3" Hooker CatBack w/Aero Chamber muffler
EDELBROCK 600CFM CARB.
KN AIRFILTER
ACCEL HEI DISTRIBUTOR
160* Stat
3:73 Posi
Rebuilt 700R4
B&M Megashifter, 5" Autometer Tach w/shift lite

 

How is HC??

If its OK , lean the carb out just a little....maybe a half turn a piece.

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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
and 2 POS commuters...

R.I.P. #3
"He can see air"

[This message has been edited by Engineboy (edited September 07, 2001).]

 

RedZ,

Welcome aboard!

If you have the E4ME or E4MC Rochester, you might want to check the TPS voltage. Should be about 0.48VDC at the hot idle position. You should also check the mixture control/enrichment solenoid adjustment. An old dwell meter works well for this, since it is basically a duty-cycle meter. Adjust the control to the low end of the range, and you should be able to call the carburetor good. That's assuming that the float level is correct and the oxygen sensor is functioning. The ECM requires an accurate reading from the TPS, coolant temperature sensor, and oxygen sensor to adjust the mixture. If the O2 sensor is getting weak, you'll very likely have a rich mixture. You should also make sure the coolant temperature sensor is operating. That can be tested with an ohmmeter.

Set the ignition timing close to the stock setting and make sure the EGR is functioning if the HCs are also high.

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Later,
Vader
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"Click - Click - BOOM!"
Adobe Acrobat Reader

 

Thanks a lot for all of the replies. Before I went for my last test, I put in 2 bottles of dry gas, which I think does the same thing as alcohol. I've checked the TPS and the M/C selenoid. The HC was within limits. The car also seems to be running a little sluggish. I'll hafta go back and check the oxygen and coolant sensors.

Thanks for the help guys.....