California Smog

[mrzim4]

I have a 1986 Silverado, I've gotten it tested 4 different times now and in this process have replaced the cat, the o2 sensor, muffler, air filter, oil and oil filter, and I've had the carb tuned. Anybody have any suggestions on how to pass? I still have August tags on my baby since I can't get her to pass..

[bd]

Welcome to the site from Central California!!!

It's always painful when your vehicle fails a smog inspection, especially when it's a daily driver (in California)...

...but "what" failed exactly - HC, CO, NOx, or visual?  And, at what RPM?  Which engine? 

Who diagnosed the list of "stuff" that was replaced?  Who did the repairs?  Did the same shop smog it each time?

Without accurate information about the tailpipe emissions during the test - and specifically 'what' about the vehicle failed - it's kind of difficult to provide a sensible answer.  Post the MAX/MEASURED from the machine printout for each gas, both at idle and at cruise RPM, so we can focus our responses and provide some insight.

[mrzim4]

Its the 305 engine, the smog paper work doesn't have an idle section but there is a 15 and 25 mph

RPM-CO2%-O2%-HC-CO%-NO
1380-12.4 - 0.1 - 92 - 3.88 - 44
1073-13.9 - 0.1 - 112 - 1.41 - 32
Tops section is 15 mph bottom is 25. I've done most of the repairs myself and three out of the four times were one shop and the fourth was another, thanks for all help.

[mrzim4]

Little more info..couldn't find an EGR valve anywhere so I cleaned it out enough that it actually works now. My dad is pretty sure that it is either the carb our the charcoal canister, he's saying carb because that is the only thing thats been replaced since the last time it passed smog, and his friend (GM mechanic and also original owner of this truck) thinks it might be the canister.

[bd]

It runs a little rich at 15 MPH, then leans out slightly at 25 MPH (still rich)... 

A few possible causes:
* rich idle mixture adjustment
* heavy carburetor float (inspect for blistering - squeeze lightly and check for oozing fuel)
* slightly high float level
* misadjusted MC solenoid
* leaking fuel well plugs
* MAP sensor slightly out of range
* grossly saturated EVAP canister (take it off and weigh it - should weigh no more than ~3 lbs)

HC increases at 25 MPH:
* verify the initial timing - decrease by as much as 3° below spec
* spark plugs
* verify that your EGR valve is not leaking past its seat (invert the EGR and spray a little penetrating oil around the pintle and make sure no penetrant visibly leaks past the seat into the adjoining chamber)

[454Man]

It runs a little rich at 15 MPH, then leans out slightly at 25 MPH (still rich)... 

A few possible causes:
* rich idle mixture adjustment
* heavy carburetor float (inspect for blistering - squeeze lightly and check for oozing fuel)
* slightly high float level
* misadjusted MC solenoid
* leaking fuel well plugs
* MAP sensor slightly out of range
* grossly saturated EVAP canister (take it off and weigh it - should weigh no more than ~3 lbs)

HC increases at 25 MPH:
* verify the initial timing - decrease by as much as 3° below spec
* spark plugs
* verify that your EGR valve is not leaking past its seat (invert the EGR and spray a little penetrating oil around the pintle and make sure no penetrant visibly leaks past the seat into the adjoining chamber)

bd is awesome

[zieg85]

[/quote]
bd is awesome
[/quote]

I was thinking the same thing.

[mrzim4]

It runs a little rich at 15 MPH, then leans out slightly at 25 MPH (still rich)... 

A few possible causes:
* rich idle mixture adjustment
* heavy carburetor float (inspect for blistering - squeeze lightly and check for oozing fuel)
* slightly high float level
* misadjusted MC solenoid
* leaking fuel well plugs
* MAP sensor slightly out of range
* grossly saturated EVAP canister (take it off and weigh it - should weigh no more than ~3 lbs)

HC increases at 25 MPH:
* verify the initial timing - decrease by as much as 3° below spec
* spark plugs
* verify that your EGR valve is not leaking past its seat (invert the EGR and spray a little penetrating oil around the pintle and make sure no penetrant visibly leaks past the seat into the adjoining chamber)

Awesome, thanks, now I have a list instead of just guesswork.

[Edahall]

When I was in CA, I used to use corn fuel (aka E85) in one of my cars that always had a very difficult time with emissions.   Just make sure that you do this on an empty tank so you can fill it back up with dino fuel before the corn fuel eats up everything.