Car shudders/CEL flashing when I accelerate at about 50 mph

Discussion in 'LS, LT, LTZ' started by Allie7, Nov 28, 2019.

  1. Allie7

    Allie7 Member

    Age:
    46
    Posts:
    49
    Likes Received:
    0
    Joined:
    Apr 1, 2015
    My 2010 cobalt has 136k miles. Husband says he heard an engine knocking noise but mechanic and I don't hear anything. Few weeks ago car lost power and I felt a pulsating/knocking vibration through the steering wheel while accelerating on the freeway, for 7 seconds or so, and then I regained power although the power felt a bit weak from time to time after that. A week later it happened again when I was accelerating up a slope, only this time CEL flashed at me for the 10 seconds or so; I couldn't go above 15 mph and then my car pulled out of the issue once more. The dealer found nothing amiss after the first incident. After the 2nd one, the dealer pulled a code(s?) and found shot spark plugs and 2 ignition coils that needed replaced. Well, $465 later and issue is occurring once more. This time I gunned the pedal at 50 mph, felt my engine lose power, CEL started flashing, and I turned around. Engine shuddered the entire time and barely stayed alive while I was stopped, waiting to do a u-turn to my nearby home. I have an appointment at the dealer tomorrow but am terrified they won't be able to get to the root of the problem.

    What does this sound like? Could it even be a bad engine mount, loose or disconnected hoses on or around the engine, VVT, timing chain, idle air control valve, MAF sensor air leaks, throttle by wire, bent valve, or other?

    How can I get my mechanic to get to the root of the problem? Should I take it to an indepdent mechanic instead of the dealer? Should I take it to Auto Zone first and get the codes read?
     
  2. Dabs

    Dabs Junior Member

    Age:
    36
    Posts:
    7
    Likes Received:
    1
    Joined:
    Nov 19, 2019
    Location:
    USA
    Does it feel like it's running on 3 cylinders? Not literally, but the feeling? I had something similar when I replaced my injectors. Turned out to be the vacuum line to the throttle-body. Turns out I must have unlocked the clip when working. So I removed the line, cleaned it up and put it back on. Engine stopped shuttering instantly. Could be different, but I hope this helps troubleshoot.
     
    Allie7 likes this.
  3. Allie7

    Allie7 Member

    Age:
    46
    Posts:
    49
    Likes Received:
    0
    Joined:
    Apr 1, 2015
    Thank you. It does kind of feel that way. I will have the mechanic check that clip.
     
    Last edited: Nov 29, 2019
  4. Allie7

    Allie7 Member

    Age:
    46
    Posts:
    49
    Likes Received:
    0
    Joined:
    Apr 1, 2015
    Today the dealer observed misfires are occuring primarily in 1st cylinder (piston). He found a lot of carbon buildup in throttle body so cleaned it out. Also cleaned debris off fuel rails and cleaned fuel injectors. They took my car for a 45 mile drive, pushing the gas pedal down hard...no issues. They gave me a good-sized discount, just to be nice. :) Fingers crossed this solves the problem.
     

Share This Page