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99 Ram Van Won't Pass Smog (in CA)

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  • 99 Ram Van Won't Pass Smog (in CA)

    very high NO. like 10-12X the average for my vehicle. I've read and I've been told that I'm running too lean. I can't very well control that since the computer handles that ratio. I've failed smog 4X now and it's getting old. Here is what I've done:
    New Cat
    New O2 Sensor (Only 1 upstream sensor on the Van)
    New Oil
    New Air Filter
    New PCV valve
    New Plugs
    New engine coolant (15%) with Water Wetter and water mix
    Cleaned the Crank Case breather and tubing
    Cleaned intake and air filter housing
    Cleaned the Rotor and inside the cap terminals
    De-greased the motor

    These CNG vans have NO EGR VALVE, so it cannot be cleaned.

    NO is created when the combustion chamber is over 2500 degrees F. Adding more fuel should cool the cylinders, but I don't know how to make that happen. My CO = 0.0. The tech says if I raised this to .04 like the average, I'd probably have enough fuel to cool the combustion chamber so my NO would decrease to a passing value. He did not know how to do this on my CNG and did not want to try it.

    Any ideas besides registering it out of state?

  • #2
    Wild guess, it almost passes nox at 25 mph and has much higher nox at 15 mph? . Are you SURE you have no vacuum leaks ? Are you sure all injectors are flowing good ? , what do the fuel trims look like ? . Where did you find a cat. for the cng model ? That used to be the big problem on cng caravans, bad cat, will not pass nox, and no availability of the cng model cat ( was NOT the same as a gasoline engine cat on the caravans )


    • #3
      Calling Dr Smog (Larrycng)


      • #4
        you could try unpluging the fuel rail pressure sender than you can change the fuel pressure at the hp regulator to change the mix dont know if you can get away with that out on the shaky side. you might try a water injection system as that cools the chamber just a guess. you can make the fuel rate variable buy hooking a rheostat up to the fuel rail sender wires I dont remember the ohm value.for some reason I want to say 132 but check across the pins on the sender.the highest will be the ohm value you need. it could be that the fuel rail sender is bad. the first thing I would is turn the rail pressure up min 10 pound increments and see if it gos down in nox as if the sender is bad the computer cant see the rail pressure so it wont change the pulse withe and you will be able to change the mix by fuel pressure higher is richer. these senders are a big problem as there none left in stock anywhere in dodges system. I have been talking to a mfg about making a run and they want to make a min 1000 run. but that is a lot of money for something that will sit on the shelf for a long time I will still have a pile of them when I die. I think you are wrong on the egr valve look below the dist on the back of the motor. everyone I have had had one it is small and has a tube feeding it from the exhaust. of course the ones sold under carb might be different.
        Last edited by cowboy; 09-15-2015, 09:52 AM.