Power loss on the highway
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Cadillac Allante Forum Discussion, Power loss on the highway in Past Cadillac Vehicle Discussion; I tried a targeted search and did not find something here in the group. I was driving on the highway ...
  1. #1
    bruce's Avatar
    bruce is offline Cadillac Owners Member
    Automobile(s): 92 Allante (205K), 91 Allante (135K)
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    Unhappy Power loss on the highway

    I tried a targeted search and did not find something here in the group. I was driving on the highway last week when all the sudden the car started loosing speed, the RPM's dropped drastically and it sound like it had a jake-brake. When I pulled over, the car idles fine and runs up to about 2,000 rpm without issue. Once you get over 2200, it drops again quickly, running very rough, even backfired a couple of times, and will die if you don't back off the accelerator. I was able to drive it off the highway, even drove it up the ramp on the tow truck. Anything at highway speed no longer possible. I tried to pull error codes, but nothing is current or past. Engine light never came on at anytime through this ordeal. Has anyone had this issue before? Any ideas of what I should be checking?

    Thank you

    '91 Allante, pearl white with neutral interior. 4.5L with 133,000 miles.

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  3. #2
    nbaum is offline Cadillac Owners Member
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    Re: Power loss on the highway

    PCM maybe? I would check the fuel pressure as well.

  4. #3
    carnut is offline Cadillac Owners Master
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    Re: Power loss on the highway

    Unless you know the mileage on the fuel filter, replace it. (not an Allante specific part) Sounds to me to be a fuel delivery problem. A partially plugged filter will act this way. Limiting top speed. The backfiring, I believe, is because the engine is running too lean. A restricted filter will not set a code.

  5. #4
    bruce's Avatar
    bruce is offline Cadillac Owners Member
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    Thread Starter

    Re: Power loss on the highway

    Thank you. I will give the fuel system a check this weekend!

  6. #5
    carnut is offline Cadillac Owners Master
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    Re: Power loss on the highway

    And the verdict was????

  7. #6
    carnut is offline Cadillac Owners Master
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    Re: Power loss on the highway

    I guess he passed away!!?

  8. #7
    David is offline Cadillac Owners Fanatic
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    Re: Power loss on the highway

    It could also be the catalytic converter 'dying'....

  9. #8
    bruce's Avatar
    bruce is offline Cadillac Owners Member
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    Re: Power loss on the highway

    Sorry guys, two jobs and little free daylight have prolonged this process. I had a chance to change the fuel filter last Friday and unfortunately, not a positive result. I have not doubt it was time to change but that did not cure my problem. I have noticed a small rubber hose in that area that has a broken connector on the end that may be from the fuel tank lines - maybe a return line of some sort? It is dry and hard to determine if it has a residual fuel smell but not sure exactly how to get to where it may go. I had just filled the fuel tank so it has about 20 gallons and will be hard to drain to drop. I may rent a car this weekend and visit my favorite pick-a-part that still has one on the lot and see what I can find out.
    Thank you for your help and I apologize that I have not responded sooner.

    ----------

    Would anyone know of a proper Allante mechanic in the northern California area? I have taken the book with the car to a couple of local, well reviewed mechanics, and not very satisfied with the results...

  10. #9
    carnut is offline Cadillac Owners Master
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    Re: Power loss on the highway

    Now the fuel pressure needs checked at idle and as driven. Now that we know the fuel is not restricted, I think we have a weak pump. Unfortuately its in the tank!

  11. #10
    ppaulson is offline Cadillac Owners Member
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    Re: Power loss on the highway

    Might be the cadalatic converter

  12. #11
    bruce's Avatar
    bruce is offline Cadillac Owners Member
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    Re: Power loss on the highway

    Well, I finally took the plunge after trying everything I was able to reach and work on. I took it to the local mechanic to have the fuel pump replaced and after they made a few checks, that was not the problem. $650 later I have a new catalytic converter and she is running like a top! I sure hated seeing her just sit there waiting for some love and attention, and looks like it will be a little road trip this weekend.

    Thank you all for your help,
    B

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    I have a '92 with over 200,000 miles on it and haven't replaced the catalytic converter (just about everything else though!) so I just couldn't get it through my head that was it. Hopefully it will last for a long time to come

  13. #12
    David is offline Cadillac Owners Fanatic
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    Re: Power loss on the highway

    The 'cat' converter was my first guess, as well. My '92 has 105,000 miles and still has the original converter; I replaced the entire exhaust system several years ago with the exception of the converter. One of these days.....

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