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Thread: 1990 deville 4.5 trouble code air management fault?

  1. #1
    dallasj is offline Cadillac Owners Member
    Automobile(s): 1990 Sedan de Ville 1995 eldorado 2000 buick century
    Join Date
    Aug 2006

    1990 deville 4.5 trouble code air management fault?

    here it is if anyone can help it would be greatly apprieciated i have a 1990 sedan de ville with a 4.5 133k the vehicle runs fine but not up to the standards for the emissions here in georgia. the ses light is on and the code was secondary air injection & air management ? anyone have any ideas?

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  3. #2
    chevelle is offline Cadillac Owners Enthusiast
    Join Date
    Jul 2005

    Re: 1990 deville 4.5 trouble code air management fault?

    The air management valve is located on the right hand (rear) valve cover. Look at the plumbing for it to make sense. There is a hose from the air pump to the valve. The first stage of the valve either diverts the air to the air cleaner or sends it to the second stage of the valve. The second stage of the valve either sends the air to the exhaust manifolds or to the catalytic converter.

    When the engine is started cold the air is switched to the exhaust manifolds. After the engine has warmed up for several minutes the air should switch to the catalytic converter.

    You can disconnect the hoses at the valve and see if air is coming from the pump, if it is being diverted to the air cleaner or if it is going to the heads or catalytic converter. No real easy way around this. The code indicates that the air valve is not switching correctly or that there is no air supply to the valve. It cannot tell exactly what is wrong just that air is not going thru the system.

    Possibly the air management valve has died or something is disconnected or that there is a hole in a hose or pipe.

    If passing an emissions test is the issue you could jerry rig the system by connecting the hose from the air pump (supply) directly to the hose/pipe going down to the catalytic converter. This is where the air would go when the engine is hot anyway so it should pass emissions testing with the air permanently routed in this direction. No one would likely know looking at the valve unless they really understand the plumbing if you move the hoses around carefully.

    Nothing will be hurt with or without the air system operating. I just adds supplemental air to the exhaust to make the catalytic converter more efficient. When the engine is cold the air goes into the exhaust manifold so that both the front and rear beds of the catalyst have enhanced oxidizing capacity (extra air with extra oxygen). When the engine warms up the air just goes to the rear bed of the catalyst (via the metal pipe that goes into the cat mid way down the body of the cat) to allow the front bed to see stochiometric air fuel ratio (with no extra oxygen) and to force all the supplemental air to the rear bed only to enhance the oxidizing capability of the rear bed only.

    A little bit of investigation and following the hose routings and seeing where the air is pulsing out with the engine idling should give you an idea of what is wrong. If the air is always being dumped to the air cleaner (basically a default mode to get rid of the air or dump it overboard) it means that the system is either detecting a fault and dumping air to protect the cat or that the air management valve is failed...or a fuse is blown not supplying power to the valve, etc....

    Check it out and post back.

  4. #3
    orangecountycruiser is offline Cadillac Owners Member
    Automobile(s): Cadillac Coupe de Ville '90
    Join Date
    Jul 2009
    Potsdam, Germany

    Re: 1990 deville 4.5 trouble code air management fault?

    Hi all,

    I have the same problem with my 90s Coupe De Ville. Nowhere to find a new or used air management valve for the 4.5 : (

    Now I will ask my garage if they, by the help of chevelles instruction, my problem can be solve.

    Greetings from Germany, I will post back



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