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David H
David H, GM master certified
Category: Chevy
Satisfied Customers: 2678
Experience:  Cadillac Technician 18 years cadillac dealer.ase master master certified
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2005 Chevy Trailblazer: jerking..engine light will start flashing

Resolved Question:

I have a 2005 Chevy Trailblazer and it is jerking when driving it and at an idle and sometimes the engine light will start flashing. what wrong with it.
Submitted: 6 years ago.
Category: Chevy
Expert:  David H replied 6 years ago.
A flashing check engine indicates an engine misfire severe enough to damage the catalytic converter.The jerking while driving indicates an ignition system misfire.This could be a defective spark plug,spark plug boot or ignition coil.A scan tool can be used to find which cylinders are misfiring.
Customer: replied 6 years ago.
It started acting up when we were hauling a piece of equipment and only doing 55 mph. would that of put strain on it and we think they are the original spark plugs and wires. we got it with 48,000 miles and now there is 114,000 miles on it.
Expert:  David H replied 6 years ago.
The spark plugs are recommended to be replaced at 100,000 miles.This engine does not have plug wires just plug boots attaching each coil to each spark plug.I would suggest replacing the spark plugs to start since they are at the maintenance schedule.The misfire could also be caused by a failed ignition coil or boot.Hauling a piece of equipment could have strained weak or carbon tracked spark plugs.
Customer: replied 6 years ago.
Is it easy to replace the spark plugs and coils.
Expert:  David H replied 6 years ago.

Yes,the spark plugs and coils are very easy to replace on this engine.Here is the replacement procedure.


Ignition Coil Replacement

Removal Procedure

  1. Remove the air cleaner outlet resonator. .
    Object Number: 725541  Size: SH

  2. Disconnect the ignition coil connectors (1) from the ignition coils.
  3. Remove the retaining bolts (2) from the ignition coils.
    Object Number: 725545  Size: SH

  4. Remove the ignition coils (1) from the engine.

Installation Procedure

    Object Number: 725545  Size: SH

    Important: Make sure that the ignition coil seals are properly seated to the valve cover.

  1. Install the ignition coil (1).
    Object Number: 725541  Size: SH
  2. Install the ignition coil retaining bolts (2).

    Tighten the ignition coil retaining bolts to 10 N·m (89 lb in).

  3. Replace the ignition coil connectors (1).
  4. Install the air cleaner outlet resonator.


Customer: replied 6 years ago.

what signs would show wear on the coils and spark plugs and boots and what r the coils connected to

Expert:  David H replied 6 years ago.
The coils won't show wear,they have to be tested using a computer scan tool.The boots will have cracks in the rubber or carbon tracks inside the boot.The spark plugs would have carbon tracks or excessive spark plug gap due to wear.The coils are connected to the boot then the boot is connected to the spark plug.The carbon tracks look like a black line or crack in the plug insulator that won't clean off.If a plug is carbon tracked then the plug boot needs to be replaced.
Customer: replied 6 years ago.
Do auto part stores carry coils and spark plugs and do you know how much they cost.
Expert:  David H replied 6 years ago.
Yes most auto parts stores carry spark plugs and coils.The spark plugs are about $10.00 each.The coils are about $200.00 each.The coils are not a normal wear item and do not fail very often.The coils should be diagnosed with a scan tool before replacement.The plugs and boots should be replaced for normal maintenance.
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