4.9 Problems at Wide Open Throttle
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HT4100 4.1, 4.5, 4.9 Discussion, 4.9 Problems at Wide Open Throttle in Cadillac Engine Technical Discussion; I've got a 91 Deville with 210,000 kms whatever that equates to in miles, and it runs fairly well and ...
  1. #1
    97EldoCoupe's Avatar
    97EldoCoupe is offline U.S. Patent #8,740,532 - www.studkit.com
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    4.9 Problems at Wide Open Throttle

    I've got a 91 Deville with 210,000 kms whatever that equates to in miles, and it runs fairly well and all, tuned up correctly, but at WOT when the engine is warm it wants to give out. I changed the fuel filter, checked the pressure which is between 38 and 42 PSI, cleaned the throttle body, changed the TPS (now has a new one), new cap and rotor, good plugs and wires, and I'm stumped. It's smooth by crusing speeds but when I want to accelerate sometimes I can hardly get it up to 50 MPH, unless I let off the gas a bit then it begins to pick up speed- slowly. When floored, it surges- all of a sudden wants to go but then nearly stalls. It keeps doing this and I can't figure out what's wrong- until I change my head gaskets on my 97 Eldorado, this is my only form of transportation and I don't want to end up stuck somewhere.

    Any ideas on what's causing this problem at WOT? All comments are welcomed.

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    carnut is offline Cadillac Owners Master
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    Re: 4.9 Problems at Wide Open Throttle

    Restricted exhaust. Cat. Converter coming apart internally. A good muffler shop can determine if Cat. is the culprit.

  4. #3
    HUF's Avatar
    HUF
    HUF is offline Cadillac Owners Connoisseur
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    Re: 4.9 Problems at Wide Open Throttle

    Quote Originally Posted by carnut View Post
    Restricted exhaust. Cat. Converter coming apart internally. A good muffler shop can determine if Cat. is the culprit.
    Could be. A bad one would rattle when you hit it with something.

  5. #4
    97EldoCoupe's Avatar
    97EldoCoupe is offline U.S. Patent #8,740,532 - www.studkit.com
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    Re: 4.9 Problems at Wide Open Throttle

    Found the problem- the simplest thing you can imagine that I overlooked- dirt in the fuel tank around the pick-up screen/sock/whatever it's called. Changed the tank (since the other one was rusty) and cleaned the pick-up with carb-cleaner and an air hose and the car's working perfectly now- no hesitation, no bogging, just pure Cadillac power.

    Thanks for the replies.

  6. #5
    thu's Avatar
    thu
    thu is offline Cadillac Owners Connoisseur
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    Re: 4.9 Problems at Wide Open Throttle

    I had a similar problem in my 93 Deville. Solution (after replacing the FPR and fuel filter which had no effect), was to replace the entire gas tank, fuel pump included. Cost was about $50 for the entire assembly from the junk yard.

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