WTF is up with this Eldo?
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Cadillac Seville / Cadillac Eldorado Forum Discussion, WTF is up with this Eldo? in Past Cadillac Vehicle Discussion; This car is about to have a rag stuffed in the gas tank... I have a 1991 Eldo with 4.9 ...
  1. #1
    the recluse is offline Cadillac Owners Connoisseur
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    WTF is up with this Eldo?

    This car is about to have a rag stuffed in the gas tank...

    I have a 1991 Eldo with 4.9 liter w/ 80k on the clock. Some time ago the fan sensor quit in the car and it overheated.

    About three months later I was doing routine maintenance and found both exhaust manifolds had developed cracks. Wound up changing both manifolds, the O2 sensors and because of it's now easy access, the starter. Was running good with 25-27 mpg in the city.

    Then the car s%#t the bed...

    Car developed a misfire (with what I believe to be a direct ground short because when all of this went down I immediately started to hear a "tapping" over the radio that would rise and fall with the engine RPM's) and threw E40 code. Changed the Hall Effect switch. Continued to run rough. Changed plugs with standard Delco's #6 being completely cracked and #5 wasn't even getting spark, so I also changed the cap, rotor, ICM, coil, and wires (figuring that would fix the ground fault, it didn't).

    Still runs rough (sounds like it runs on 7 cylinders) gas mileage is in half and it still has the "tapping" over the radio. Just recently threw E46 (right to left bank fueling difference) and E48 (EGR problem). Can the EGR problem be the issue with car from the get go (outside the spark plug being cracked) and just now trip the computer?

    The car has an aftermarket amp and radio that have been in the car close to 5 years now so maybe the "tapping" is coincidence, but it didn't do it prior to all these problems.

    Any help is appreciated as I am seriously looking drive this thing off of a cliff.

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  3. #2
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: WTF is up with this Eldo?

    I doubt this is the problem, but look down the TB and you'll see 2 EGR tubes staring back at you. If they are carboned closed, rod them out. Also be sure that the EGR valve itself is not stuck partially open. That WILL cause an idle problem or a stall.

  4. #3
    the recluse is offline Cadillac Owners Connoisseur
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    Re: WTF is up with this Eldo?

    Checked the TB and the carbon buildup wasn't that bad, but cleaned it out none the less.

    On the EGR, I noticed it has a vacuum controlled switch or sensor; any possibilities of this being a problem?

    Also, with it throwing the "Left to Right Fueling Imbalance" code and running crappy, could I possibly have something wrong with an injector?

    Just questionings, thanks guys...

  5. #4
    ewill3rd is offline Cadillac Technician
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    Re: WTF is up with this Eldo?

    You need to isolate the faulty cylinder and do tests to identify the problem related to that cylinder.

    Attacking the whole engine is going to cost you a lot if you keep guessing.

    If you have a few basic tools I can tell you how to pinpoint the misfire.

  6. #5
    Necrosan is offline Cadillac Owners Enthusiast
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    Re: WTF is up with this Eldo?

    Not to hijack the O.P.s thread, but I'd love to hear those tips ewill3rd.
    I have a slight misfire in my 94 Eldorado and can't figure out what's causing it for the life of me. New plugs & wires didn't fix it...

  7. #6
    the recluse is offline Cadillac Owners Connoisseur
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    Re: WTF is up with this Eldo?

    ewill3rd, I would love the help and I have more than the basic tools, so throw it at me what you got.

    I had to attack the whole engine at the time due to the damage the overheating had caused. Most everything I replaced had to be as there was a code behind it, such as the O2 sensors, hall effect switch, and the like. I was, however, hoping that replacing all of this would have fixed this by now.

    Now, I show an EGR code, so...

    Thank you for your time.

  8. #7
    ewill3rd is offline Cadillac Technician
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    Re: WTF is up with this Eldo?

    This trick I learned in the pre-OBD II days and it works great.
    You need a length of vacuum hose, maybe a foot or two of I think 7/32".
    It works good to have some old spark plugs too and a hammer or vice and some safety glasses are a good idea for at least part of it.
    Then you need a 12V test lamp, any type.
    You can use a bench vise or a hammer but take about 4 plugs (depending on how many cylinders you have) and crush the porcelain insulators. keep the tower with the cable end on it and throw the threaded part away.

    Cut the vacuum hose into about 3" lengths and slip the spark plug ends into the vacuum hose, they should fit pretty snug if I guessed the size right.

    Now go do the distributor or the coil pack and remove every other plug wire, don't make 8 and do them all, the sparks will jump everywhere and it won't work.
    Remove one wire at a time and slip the open end of the vacuum hose over the coil tower end and then snap the plug wire onto the adapter you just made.
    Install one on every other plug wire so you have a good air gap between them.

    If the misfire is steady the next part is easy, if it has to be under a load you need to take some safety precautions so you don't run yourself over and get an assistant with a brain that won't kill you.

    Connect your 12V test lamp clip to ground and then as the engine is misfiring touch the probe to the vacuum hose.
    The hose has enough carbon content to carry the spark and the test light will conduct it away to ground.
    Monitor the engine rpm. If it drops then that cyilnder was firing, if it doesn't then that is your bad cylinder right there.

    Don't put your hand close to the vacuum hose or you'll get hit, and sometimes it is fun to watch the spark jump to the test light.

    Remember a spark has tons of voltage but almost no current so it won't hurt the test light at all.
    It is just an alternate path to ground.

    If you don't find the misfire, shut the engine down and swap to the other 4 wires, then redo the test until you find the culprit.

    Once you know you can do more tests to isolate the cause. Fuel injector, loss of compression, etc... this helps you narrow it down.

    I'll post more later, they just locked the shop and I have to get out before they lock the gate!!!

  9. #8
    the recluse is offline Cadillac Owners Connoisseur
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    Re: WTF is up with this Eldo?

    Thank You, I will look into these things as soon as I fix the plenum and A/C Pressure Sensor on my 2002 STS.

  10. #9
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    dkozloski is offline Cadillac Owners 10000+ Posts
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    Re: WTF is up with this Eldo?

    Spray water on the exhaust manifolds with a spray bottle. The dead cylinder will stay wet and the live ones will boil off the moisture. In a pinch you can spit on the manifolds to get the same result. Why use a simple plan when a complicated one will do the job?
    Don't mess with Binky Bear!


  11. #10
    the recluse is offline Cadillac Owners Connoisseur
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    Re: WTF is up with this Eldo?

    no offense to ewill3rd, but that last response is classic

    Will look into both...

  12. #11
    ewill3rd is offline Cadillac Technician
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    Re: WTF is up with this Eldo?

    No offense to my good man Koz who knows his stuff... but if you can SEE the manifold His plan would certainly work.


    I never said my suggestion was the only way.
    I ain't too proud to admit there are other things too, I like to play with tools and see sparks

  13. #12
    the recluse is offline Cadillac Owners Connoisseur
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    Re: WTF is up with this Eldo?

    Quote Originally Posted by ewill3rd View Post
    No offense to my good man Koz who knows his stuff... but if you can SEE the manifold His plan would certainly work.
    Yeah the rear manifold will be the issue..

    , I like to play with tools and see sparks
    Yeah me too :grunts like Tim Taylor:

    When I was replacing the spark plugs I noticed that #6 wasn't sparking (no signs of burn) but was getting gas even after new wires, cap, and rotor, and such...I could smell gas, but it wasn't drowning in it.

    How does one test the injector?

  14. #13
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: WTF is up with this Eldo?

    Listen to it with a stethoscope. You should hear it tick tick tick just like the others.

  15. #14
    the recluse is offline Cadillac Owners Connoisseur
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    Re: WTF is up with this Eldo?

    What if its dirty or clogged or damaged from heat? Would it still tick but not inject gas or what?

    Never been a FI guy, always been a carburetor/supercharger kind of guy, so sorry if my questions seem trivial...

  16. #15
    ewill3rd is offline Cadillac Technician
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    Re: WTF is up with this Eldo?

    There are so many detergents in modern gasoline it is almost impossible for an injector to get "dirty".
    They can plug up but usually there is a screen in the top of the injector that collects any debris that got past the fuel filter.
    At any rate with plastic tanks I never see "plugged" injectors.
    If you have good spark and provided you can reach the connectors you can do a similar "rpm drop" test by disconnecting one injector at a time.
    On most newer engines this will set a code and it can disable the injector for a few moments after you reconnect it so it isn't a great one.
    They make "noid lights" to test the control circuit to the injector.

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