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SMOG (Pass but barely)

Discussion in 'The Garage' started by sandawgk5, Mar 6, 2007.

  1. sandawgk5

    sandawgk5 3/4 ton status

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    I just got the K5 smogged today and I passed but my readings are still really close to not passing. HC are still high and I just put a brand new exhaust on including a new CAT that is rated for an engine larger than mine by .2l so it is close and the oil was changed not 30 min before the test.

    I had the cat hot and I kept it idleing while I was waiting for my turn on the smog dyno. Also CO is up and the guy says that is an indication of running rich?

    Here is the data from today
    View attachment smog2007.bmp

    And here is the sheet from 2 years ago
    smog.jpg

    Any ideas guys and gals? Is it time to go through the engine?

    Oh I do not have to smog again until March 2009

    Thanks

    Ira

    smog.jpg
     
  2. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Sounds like it is time to drop a new 6.0L in ;)
     
  3. sandawgk5

    sandawgk5 3/4 ton status

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    Ya I like that idea but my wallet doesn't:doah: . A 6.0L with a 465 would kick ass though in my book:D .

    Ira
     
  4. 4by4bygod

    4by4bygod 1/2 ton status

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    Ira.. is this from the 87 in your profile?

    Looks like your HC reading @ 25 MPH only went up a bit.. is the o2 sensor still the same one from two years ago? that could be getting fouled..

    HC is the presence of unburned fuel in a carbon form.. maybe if you got a new o2 sensor, and maybe upgraded the ignition ( increased spark, hotter plugs ) you might bring those numbers down.. the idea being to insure you get the correct amount of fuel metered, and then consume as much of that fuel as efficiently as possible.. If the HC comes down, I suspect the CO numbers will come down too..

    it's also possible that the thing "loaded up" from idling - were you keeping it at a high idle when you were in line? that will do it too..

    My TBI motors have always done best when I changed the oil a few days beforehand, made sure the ignition system was good to go, and I got thing as hot as I could on the freeway before I hit the station.. oh yeah, if you can, go to shell for gas beforehand.. they have some good detergents in their fuel that will help..

    just some ideas..
     
  5. sandawgk5

    sandawgk5 3/4 ton status

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    Ya it was idling high fro some reason around 1100. That could have done it eh? I guess next time I will hit the highway for a while before I smog it. I could not get the thing off of high idle for some reason. It started doing it at the desert on Sunday before I left.

    Everything is the way I got the truck back in 2001 except for the exhaust that I put on after the Y-pipe so my 02 sensor might not be tip top. I was going to put a WBO2 sensor on asI have plans to get an EBL and I wanna data log and also let the ECU learn on its own:D .

    It probably would not hurt to do plugs wires cap and rotor as those are about 4 years old:doah: .

    Ira
     
  6. sandawgk5

    sandawgk5 3/4 ton status

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    Another thing the timing was 3 BTDC and 2 years ago it was 0 could that cause a shift in the numbers?

    And anyone in East County down here the guy at the smog station by the DMV says if it will fit in the garage he can smog it on his dyno. Says 42s are no problem:D .

    Ira
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    Fix the high idle problem, then worry about emissions.

    If it's idling high, something is wrong that is likely to lead to worse emissions.
     
  8. sandawgk5

    sandawgk5 3/4 ton status

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    What causes high idle? It is a TBI 350 and the idle does come down I think that maybe I just did not do a good enough "warm up run" before I went to the smog station.

    Ira
     
  9. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    Pull the IAC motor and check for coking. If the IAC seat is coked with carbon it will have a high idle.
     
  10. dyeager535

    dyeager535 1 ton status Premium Member

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    Make sure you've got the right thermostat in it, you should never have to worry about it being "up to temp". 195* is 195* whether at idle or cruising.

    Higher engine load tends to heat up the O2 sensor and Cat converter, if either isn't getting hot enough, they aren't effective, so that's why people talk about a good freeway run RIGHT before emissions testing. Good ten minutes on the freeway, drive it directly into the smog station and have it tested. The longer you wait in line, the less likely the previous added load is going to make a difference.

    High idle can be caused by a few things...IAC, throttle stop, coolant temp sensor.

    If the idle takes awhile to come down, but DOES get back to normal, I'd first check (not replace) the coolant temp sensor, and make sure that it is accurately reporting the temperature to the ECM. That means you also need to make sure the engine is getting up to operating temp. If you have a stock gauge and a scanner, you can check both the gauge and the sender. If they duplicate each other as the temp climbs, then both are likely working correctly. If they aren't the same, one of the two is wrong.

    I would expect if it were an IAC problem to never correct itself. Problem correction after running for awhile leads me to look at things influenced by temperature.
     
  11. K-5 Bomber

    K-5 Bomber 1/2 ton status

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    At the risk of sounding stupid...what's IAC? And while I'm asking... I have to take my wife's '86 for smog at some point. It doesn't heat up either. Already replaced the T-stat only to test the old one and find that it was opening at 195* as it was supposed to. What else would lead to such a cool running engine?
     
  12. dyeager535

    dyeager535 1 ton status Premium Member

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    Idle Air Control.

    It's an electric device controlled by the ECM that the ECM opens or closes to make sure the right amount of air enters the engine at idle/decel and I believe stall conditions. In construction, it is simply a rounded or pointed "nose" that fits into a round or pointed cavity in the throttle body. The further in it is, the less air bypasses the throttle plates. Further out, more air.
     
  13. K-5 Bomber

    K-5 Bomber 1/2 ton status

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    So is that a TBI exclusive device? Our rigs both have Q-jets. What about the engine temp issue- any insite into that?
     
  14. vortec

    vortec 1/2 ton status

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    on the rochester 220 throttle body, the IAC should be located on the passenger side, towards the back, at an angle. it will have a wiring harness and the hex area used to loosen/tighten it is large and fairly soft. when i pull mine off to check it, i use a large adjustable wrench or some channel locks with duct tape on the jaws, so it won't damage the iac. there should be a little gasket between it and the tb. the pintle should move a little bit with firm but gentle finger pressure, if it's ok.

    you can pull the o2 sensor and test it with a multimeter and a propane torch. i can't remember the exact process, though. i'm sure someone on here knows exactly.
     

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