368 V-8-6-4 Advice
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500, 472, 425, 368 Discussion, 368 V-8-6-4 Advice in Cadillac Engine Technical Discussion; I own a 1981 Sedan de Ville with a 368. It's been a very good car and I have over ...
  1. #1
    tfd52 is offline Cadillac Owners Member
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    368 V-8-6-4 Advice

    I own a 1981 Sedan de Ville with a 368. It's been a very good car and I have over 230K on the clock. Within the past 6 months, the car has experienced very bad gas mileage, and a constantly "ON" Check Engine Light.

    They've checked out the wires, and distributor. The car seems to get good spark. The fuel pressure to the TBI appears normal. (Nobody wants to dig out the coolant sensor though--hehe)

    Two shops that I have taken the car to have basically given up on the diagnosis and have basically advised me to junk the car.

    Given that the car is 25 years old and maybe worth $1,200, what do you advise? I really like the car. It's the best car for driving long distances that I have ever own (and I still like to better than my 83 300SD MB, and that's saying a lot)

    What do you advise?

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  3. #2
    The Ape Man's Avatar
    The Ape Man is offline Cadillac Owners Connoisseur
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    Re: 368 V-8-6-4 Advice

    Find a mechanic who knows what he/she is doing.

  4. #3
    DopeStar 156's Avatar
    DopeStar 156 is offline Cadillac Owners Master
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    Re: 368 V-8-6-4 Advice

    Quote Originally Posted by The Ape Man
    Find a mechanic who knows what he/she is doing.
    LOL!!!

  5. #4
    CoupeDevilleRob's Avatar
    CoupeDevilleRob is offline Cadillac Owners Enthusiast
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    Re: 368 V-8-6-4 Advice

    Don't junk the car just because of what is probably a minor problem. It seems like the mechanics you took it to are just lazy and don't want to be bothered with an old car. Find a good mechanic.

  6. #5
    tfd52 is offline Cadillac Owners Member
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    Re: 368 V-8-6-4 Advice

    I appreciate the comments about finding a good mechanic.

    I don't know if other people have experienced the same thing, but many times I've found that if the mechanics can't pin down the problem in an hour or two, they're too busy to push further.

    I do own the service manual to the car and have done a lot of work to the car myself. It's just that I'm stumped at this moment, and no one that I take the car seems to be happy about working on a V8-6-4 Caddy.


    I live in the metro Washington, D.C area. Any leads?

  7. #6
    CoupeDevilleRob's Avatar
    CoupeDevilleRob is offline Cadillac Owners Enthusiast
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    Re: 368 V-8-6-4 Advice

    I would post in detail the problems you're having in the 368, 425, 472, 500 section. I'm sure there are people lurking in that section who can help you out. You seem to be familiar with the car which helps, some people post with a problem and have no clue what they are talking about. I find most mechanics to be the same way, they'd rather take a job that's a quick fix then spend a long time trying to trouble shoot a complex problem. Good luck getting it running right, whatever is wrong with it can be fixed.

  8. #7
    Bro-Ham's Avatar
    Bro-Ham is online now Cadillac Owners Connoisseur
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    Re: 368 V-8-6-4 Advice

    Hi,

    I have a 1981 Fleetwood Brougham Coupe with the V8-6-4 and I have a check engine light that comes on constantly and the mileage is bad and it seems to lose power. This car has had everything possible replaced including plugs, wires, computer, etc. My car is at my (hopefully) competent mechanic right now and I (hopefully) plan to have these issues resolved otherwise I'm yanking out the damn ancient electronics and V8-6-4 system so it can run like the normal Cadillac that I know it is (hopefully) underneath all these issues that make me hate it! My car has 236k miles on it.

    I'll let you know if I learn anything.

    Ape Man, is there an easy way to un-"compuker"-ize these 81's?

    Dave

  9. #8
    CadiJeff's Avatar
    CadiJeff is offline Cadillac Owners Connoisseur
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    Re: 368 V-8-6-4 Advice

    Have you checked the o2 sensor? is the computer throwing any codes? the car probably knows the problem just nobody is listening.

  10. #9
    The Ape Man's Avatar
    The Ape Man is offline Cadillac Owners Connoisseur
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    Re: 368 V-8-6-4 Advice

    Quote Originally Posted by Bro-Ham
    Hi,


    Ape Man, is there an easy way to un-"compuker"-ize these 81's?

    Dave
    No there isn't. If you found a junk 1980 with a 368 then at least you'd have all the parts. It's a lot of work for no gain. Better to repair the current system.

    Replacing parts without finding definite failures is a sure way to frustration.

  11. #10
    elk9300` is offline Cadillac Owners Fanatic
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    Re: 368 V-8-6-4 Advice

    If the shops can't fix this go to another shop (as was said before) or do it yourself.

    Your check engine light is telling you that something is up (as was said before)

    SOunds like something in the exhaust (O2 sensor, perhaps a bad catalytic , again something mentioned before.
    Scrapping the car because they can't fix it just show their lack of competence.

    I stopped taking my cars for state inspection at various shops because of their inability to find problems by using a combination of diagnostic tools (ie computer, vacuum gage etc.)

    In my view There are 3 different types of shops. 1.) The kind that throw parts at a car without scannning the codes on the computer. 2.) The kind that rely on the computer and don't use the old school tools like a vacuum gages. They can't even rebuild carbs properly to specification 3.) The kind that uses a combination of checking codes and diagnosis tools to solve the problem and get the car fixed faster than the first 2 shops. Theses shops exist but are harder to find

    Pull the codes. Check changes in engine vacuum at different RPMs to see if you have a blocked exhaust. You probably can do it yourself successfully.

  12. #11
    kc81cadman is offline Cadillac Owners Member
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    Re: 368 V-8-6-4 Advice

    my 81 is doing the same thing but with a fast idle that will not kick down. Check my post further down the list. Ape Man responded with a stuck idle motor or associated linkage. I also have melted wires for the coolant temp. sensor that no one has been able to remedy. I thinl I will get some thermocouple wire to replace the existing wire so it is more temp. resistant.
    KC.

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