1990 4.5l air system problem
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HT4100 4.1, 4.5, 4.9 Discussion, 1990 4.5l air system problem in Cadillac Engine Technical Discussion; is there any way to find what is causing this? Keep getting e49 and car runs real bad. No smoke ...
  1. #1
    ashunte23 is offline Cadillac Owners Member
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    1990 4.5l air system problem

    is there any way to find what is causing this? Keep getting e49 and car runs real bad. No smoke from tail pipe but idles rough and backfires no power at all.ant help would be greatly appreciated.

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    D'Elegance is offline Cadillac Owners Fanatic
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    Re: 1990 4.5l air system problem

    Might be your air diverter valve, just a guess but thats what it was on my Caddy.

  4. #3
    ashunte23 is offline Cadillac Owners Member
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    Re: 1990 4.5l air system problem

    Quote Originally Posted by D'Elegance
    Might be your air diverter valve, just a guess but thats what it was on my Caddy.
    how do you find out if it is?

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    Re: 1990 4.5l air system problem

    From the AIR pump there is a fairly large hose running to the AIR valve on the RH valve cover. It connects to the front half of the AIR valve. If you look you can see that there are two sections to the valve. The first valve either sends the AIR from the pump to the air cleaner (divert mode) or sends it to the second half of the valve. The second half of the valve switches the air to the heads/exhaust manifold or to the pipe that is going to the catalytic converter. When the engine is cold the AIR should be switched to the exhaust manifold. When the engine is warm it should switch to the catalytic converter.

    It sounds, from your description and the code, that the second half of the valve is stuck or failed causing the air to always stay switched to the exhaust manifold....that causes erroneous O2 sensor signals and fools the closed loop system into running the system too rich. You can diagnose this by taking the hose off the AIR valve that runs from the AIR valve to the exhaust manifold (just follow the hoses to see which one runs from the AIR valve to the exhaust manifold fitting) and leaving it disconnected. Plug the port to the exhaust side with a cork or something and drive the car to see if it runs OK. If so, then find out what is wrong with the AIR valve. I think that that valve had vacuum lines to it to actuate the valve if I am not mistaken. Possibly the electrical connectors from the PCM are corroded/loose or the vaccuum line is off/leaking.

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    ashunte23 is offline Cadillac Owners Member
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    Re: 1990 4.5l air system problem

    Quote Originally Posted by bbob
    From the AIR pump there is a fairly large hose running to the AIR valve on the RH valve cover. It connects to the front half of the AIR valve. If you look you can see that there are two sections to the valve. The first valve either sends the AIR from the pump to the air cleaner (divert mode) or sends it to the second half of the valve. The second half of the valve switches the air to the heads/exhaust manifold or to the pipe that is going to the catalytic converter. When the engine is cold the AIR should be switched to the exhaust manifold. When the engine is warm it should switch to the catalytic converter.

    It sounds, from your description and the code, that the second half of the valve is stuck or failed causing the air to always stay switched to the exhaust manifold....that causes erroneous O2 sensor signals and fools the closed loop system into running the system too rich. You can diagnose this by taking the hose off the AIR valve that runs from the AIR valve to the exhaust manifold (just follow the hoses to see which one runs from the AIR valve to the exhaust manifold fitting) and leaving it disconnected. Plug the port to the exhaust side with a cork or something and drive the car to see if it runs OK. If so, then find out what is wrong with the AIR valve. I think that that valve had vacuum lines to it to actuate the valve if I am not mistaken. Possibly the electrical connectors from the PCM are corroded/loose or the vaccuum line is off/leaking.

    thanks I'll give that an try today.will update after

  7. #6
    ashunte23 is offline Cadillac Owners Member
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    Re: 1990 4.5l air system problem

    that didn't work car ran even worse? any more ideas hate to pay dealer costs but looks like I'm gonna have to bite the bullet.

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    Re: 1990 4.5l air system problem

    Did you disconnect the AIR line to the exhaust manifold completely and plug the port/hose to the exhaust manifold??

    When you do that, disconnect the battery negative cable for 60 seconds and then take the car out and drive for awhile. Just taking the hose loose for a short period might not prove the point as the system has "learned" a severe fuel offset due to the erroneous air delivery. Reset that by disconnecting the negative battery terminal and drive for awhile to see if the problem is resolved.

    If not, it may be an injector sticking or failed fuel pressure regulator causing excessive richness that is "fooling" the AIR failure detection code.

    Have you checked the fuel pressure regulator by pulling the vac line off the FPR while idling to see if any fuel seeps from the FPR vacuum nipple.

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    ashunte23 is offline Cadillac Owners Member
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    Re: 1990 4.5l air system problem

    Quote Originally Posted by bbob
    Did you disconnect the AIR line to the exhaust manifold completely and plug the port/hose to the exhaust manifold??

    When you do that, disconnect the battery negative cable for 60 seconds and then take the car out and drive for awhile. Just taking the hose loose for a short period might not prove the point as the system has "learned" a severe fuel offset due to the erroneous air delivery. Reset that by disconnecting the negative battery terminal and drive for awhile to see if the problem is resolved.

    If not, it may be an injector sticking or failed fuel pressure regulator causing excessive richness that is "fooling" the AIR failure detection code.

    Have you checked the fuel pressure regulator by pulling the vac line off the FPR while idling to see if any fuel seeps from the FPR vacuum nipple.
    where is the fuel pressure regulator located tried the other things and that didn't work.could running rich hurt the catalytic converter?should I just get the whole fuel system replaced, car has 90,000 miles anyways. If this helps just got an stereo installed nothing big but might be causing the problem since they kinda happened in order. Got stereo then got problem.could the alternator not provide enough power and cause this? Is there any way to check that?

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