Engine Shaking
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Northstar Engines and System Technical Discussion Discussion, Engine Shaking in Cadillac Engine Technical Discussion; My P0300 (Misfire) code has went away but I still have a bit of shaking at idle (Park and Drive). ...
  1. #1
    jcresciSTS is offline Cadillac Owners Enthusiast
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    Engine Shaking

    My P0300 (Misfire) code has went away but I still have a bit of shaking at idle (Park and Drive). Last night when stopped at 7-11 while my friend ran inside I decided to pop my hood with the engine running and I noticed my engine was shaking and is what is causing my car to shake since the way it shakes is the way the shaking feels.

    Spark Plugs were replaced a while back with the correct A/C Delco's. I had ordered some wires from RockAuto but ended up returning them since my misfire went away.

    My friend said its normal but I know when I first got the car it was so quiet and smooth that I couldn't even tell it was on.

    What could be causing this?

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  3. #2
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: Engine Shaking

    Shaking is not normal. You should not even know it is running, nor should you have returned the wires.

  4. #3
    jcresciSTS is offline Cadillac Owners Enthusiast
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    Re: Engine Shaking

    I'll reorder them then...

    What do you think could be causing it to shake? Motor mount?

    The plugs should be the correct ones.

    The reason for returning them went like this:

    Tuesday got spark plugs changed but car still idled a bit rough

    Thursday took it to the GM dealer for a ATF Exchange and Coolant Flush, got home and ordered the wires

    Thursday picked up the car from the dealer and car ran amazing, I couldn't even tell it was on.

    Finally got wires and shipped them back because I didn't seem to have the problem anymore...problem came back but I figured it was something else causing it like a dirty TB

    I was going to go get a balance and hopefully alignment from Firestone tomorrow for $89.99 but that deal is good til Sept 12 so I guess I will wait and order the new wires.

  5. #4
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: Engine Shaking

    I assume you are talking about an engine shake at idle. My guess would be a mild misfire. Maybe try misting the wires at night before reordering them. I know they are expensive, but being 10 yrs. old (if they are original) they are due.

  6. #5
    jcresciSTS is offline Cadillac Owners Enthusiast
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    Re: Engine Shaking

    Yes, it shakes at idle, Park and Drive.

    Yeah, they were about $108 with Tax/S&H (RockAuto). I'm going to re-order them anyways, my mechanic said I most likely needed new ones since they are original.

  7. #6
    jcresciSTS is offline Cadillac Owners Enthusiast
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    Re: Engine Shaking

    Come to think of it, a better way to describe it is a shudder about every 2 seconds (give or take 1 second)

  8. #7
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    Rodney_98 is offline Cadillac Owners Member
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    Re: Engine Shaking

    Could fuel be causing this? Moisture in the system or just a bum tank of fuel?
    I'll get a bad tank of fuel in my Harley from time to time { it needs premium}. runs like Cr$% until I burn it out and get another tank.
    my two cents..

  9. #8
    Necrosan is offline Cadillac Owners Enthusiast
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    Re: Engine Shaking

    My 94 Eldorado has these exact same symptoms.
    Still working on a fix though. Plugs and wires were _NOT_ the fix.

  10. #9
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    Submariner409 is offline If it won't run, stick on fender vents
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    Re: Engine Shaking

    IF we're all talking about a pre-2000 4.6 Northstar with 4 coils check your plug wires against the diagrams. Which wire is on which coil tower is critical, and if a pair of wires is connected to the wrong coil towers that will cause a nagging miss. Google "waste spark ignition" to find out why.

  11. #10
    jcresciSTS is offline Cadillac Owners Enthusiast
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    Re: Engine Shaking

    Thanks. I'll check it out Sub

    I only use Shell V-Power, occasionally Chevron 91 Oct.

  12. #11
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    ryannel2003 is offline Cadillac Owners Connoisseur
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    Re: Engine Shaking

    I tell you my 2000 STS has always had a slight "miss" during idle in the Park and Drive position since I bought it. I had it diagnosed sometime this year and it was said to be something to do with the 2000-2001 Northstar's having a cam issues that caused the car to have the miss. I did quite a few things to try to fix it, including new spark plugs, a new intake plenum, TB cleaning, etc. to no avail. Once i finally found out what it was, I just forgot about it. Never had a misfire code. Now that I think about it, the front coil pack is my bet because when I pressure wash the motor occasionally the car misfires like crazy.

    I know this has nothing to do with your '99 N*, but your symptoms sound like mine.

  13. #12
    jcresciSTS is offline Cadillac Owners Enthusiast
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    Re: Engine Shaking

    Thanks for the info...

    I did some checking best I could, didn't want to mess anything up and not have the car run for work tonight.

    The wires look like they are in correct firing order. I was only able to about 80% of them since they were hard to pull on and I didn't want to disconnect anything.

    Here's a pic and some videos.

    Not sure what this is but it makes some sort of hissing noise (not sure how to describe it) and there is a bit of fluid on it:


    The videos are of my car idling and starting up. The chime is loud in the 1st video but you can hear how loud the engine is from inside, may need to turn volume up though.




  14. #13
    Submariner409's Avatar
    Submariner409 is offline If it won't run, stick on fender vents
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    Re: Engine Shaking

    The big fuzzy pic is the PCV valve and connector, which moves a LOT of air through the crankcase/cam cover areas to control vapor and condensation. There should be NO suction or hiss noise from there. If there is, suspect the 90 degree connector which joins the PCV valve itself with the vacuum pipe to the intake manifold.

    You can find a new connector in the "Help!" blister pack rack at your local Pep Boys or Auto Zone store. DO NOT try to fix that vacuum leak with silicone or goop. Find a new connector.

  15. #14
    jcresciSTS is offline Cadillac Owners Enthusiast
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    Re: Engine Shaking

    easy fix? It pops on and off easily.

  16. #15
    Necrosan is offline Cadillac Owners Enthusiast
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    Re: Engine Shaking

    Too easy of a fix..

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