Timing Mark bouncing around
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HT4100 4.1, 4.5, 4.9 Discussion, Timing Mark bouncing around in Cadillac Engine Technical Discussion; My 95 Cadillac deville 4.9l timing mark is bouncing around and its even bouncing crazier when i turn the heat ...
  1. #1
    kerwinswan is offline Cadillac Owners Member
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    Timing Mark bouncing around

    My 95 Cadillac deville 4.9l timing mark is bouncing around and its even bouncing crazier when i turn the heat on which make my car backfire and misfire. I have change the timing chain, the distributor and map sensor and still no luck. Could anyone help me with this one please, thanks in advance.

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    drewsdeville is offline Cadillac Owners Master
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    Re: Timing Mark bouncing around

    I would start checking for bad grounds

  4. #3
    eyekandyboats.inc's Avatar
    eyekandyboats.inc is offline Cadillac Owners Connoisseur
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    Re: Timing Mark bouncing around

    dwell variation?

  5. #4
    steelybill is offline Cadillac Owners Enthusiast
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    Re: Timing Mark bouncing around

    I believe drewsdeville has a good point. Turning on the heater would draw more current, putting a higher load on a bad ground. A voltage check of power at the distributor may show a drop when the heater is turned on. Ignition voltage would also suffer, causing a mis-fires etc. Lots of grounds on these cars. A factory manual lists them, and wiring diagram might show the faulty one.
    All this is assuming the buss voltage from the alternator is up where it should be, 13+ volts.
    Not being familiar with the 4.9, I would look on the top of the intake manifold for a ground, and if you had the manifold off, you may have missed a ground wire in there someplace.

  6. #5
    Sevillian273's Avatar
    Sevillian273 is offline Cadillac Owners Connoisseur
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    Re: Timing Mark bouncing around

    This might sound dumb but are you jumping the A and B terminals on the ALDL connector under the dash when checking the timing?

  7. #6
    kerwinswan is offline Cadillac Owners Member
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    Re: Timing Mark bouncing around

    I did jump the A and B terminals on the ALDL connector but the timing mark would not stay still. I can drive for about a mile and then the car will backfire and i will push the gas pedal to the flood and it would gain speed, and then i will pull over and turn the car off then on and go through the same problem. i told a mechanic about my symptoms and he said that my cam was bad, could he be right

  8. #7
    steelybill is offline Cadillac Owners Enthusiast
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    Re: Timing Mark bouncing around

    He could be right in one sense, the distributor gear and cam gear could be worn enough to have a loose mesh of the gears, and jump the timing around a bit. You could check that part by removing the distributor and inspecting it's gear, and with it out you should be able to see the cam gear down in there. Not uncommon for the distributor gear to wear. The wear on cam lobes shouldn't affect timing scatter, just valve lift, if that's what your mechanic meant.

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    kerwinswan is offline Cadillac Owners Member
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    Re: Timing Mark bouncing around

    Hey steelybill, i did check the wires already but im willing to check them again what would i be looking for, what would a bad ground look like

  10. #9
    steelybill is offline Cadillac Owners Enthusiast
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    Re: Timing Mark bouncing around

    A bad ground on a bolt on the engine may not be obvious. The positive way is the remove ground wires , clean the terminal lugs, the bolt etc and put them back on.
    A wiring diagram for your car would show the ground for the ignition system.
    We are right back to the idea that the best thing for you to have is a factory manual, if you don't already have one. The factory manual lists all the grounds on the car, and where they are located.

  11. #10
    kerwinswan is offline Cadillac Owners Member
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    Re: Timing Mark bouncing around

    hey steelybill

    i have notice that when i turn my headlights on that's when it actually acts up more especially at night. I'm convince that it is the ground and was wonder where to start tracing the wires

  12. #11
    steelybill is offline Cadillac Owners Enthusiast
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    Re: Timing Mark bouncing around

    That sounds like you need to check the battery voltage, with the engine off (around 12 volts) and with it running, which should be 13+ volts with a load, like lights etc. With everything electrical turned off, the alternator should be charging the battery to around 14 volts.
    If the voltage is lower than these numbers, you may have some alternator diodes out, or other alternator faults.
    Not familiar with that year, but mine ('85) has a bunch of electrical "stuff" near the battery. You might just look around for loose terminals, nuts etc, on the things mounted on the left fender well.

    The feed wire that runs everything electrical comes from the terminal on the starter, a good sized (#10 ) wire, on the same terminal as the battery cable. You might make certain that the nut is tight there, and the wires tight etc.

    How good does the starter turn the engine??

  13. #12
    kerwinswan is offline Cadillac Owners Member
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    Re: Timing Mark bouncing around

    It runs fine i had it replace earlier this year, but i will check the post to it and see if it loose

  14. #13
    kerwinswan is offline Cadillac Owners Member
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    Re: Timing Mark bouncing around

    The starter wire are tight all the wire are tight, i notice when i pull the ign 3 fuse the whole dashboard goes blank and i turn the headlights on and there's no problem when i put the fuse back in and turn rear defrost it acts up obviously the ign 3 and rear defrost is on the same circuit. what do think it could be

  15. #14
    steelybill is offline Cadillac Owners Enthusiast
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    Re: Timing Mark bouncing around

    The ignition switch likely has 4 sections, and one is for the actual ignition, and others are usually for accessories. The power to the ignition switch may be the problem (or the switch itself), since the ignition seems to suffer when accessories and lights etc are turned on, and possibly bringing the voltage down by resistance in the switch, or by the feed wire to the switch.
    The feed wire for the ign switch (on mine) comes from a fusible link near the battery, a big red wire runs to the switch from there to the switch.
    If your car has a jump-start terminal inside a plastic cover, the fusible links may be wired to that.
    You really need the manual for that year, since mine may be different in the electrical layout. I do believe you need to measure the voltage on the power wire on the distributor when you turn on the lights etc, to see if the voltage drops off from where it is without those things on.

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