We just replaced the head gasket and sealed with silicone and new gaskets. After our process was complete we discovered the engine idle would go from 1,000 rpms for 8 sec to 500 rpms 8 seconds sometimes even 350 rpms about. What did we mess up?? We already checked the status of the ignition coils they are good read 6.6 on the ohms of a voltage meter. If anyone has a check list of possible issues that would help so much. video of my explanation

  • All pipes connected properly, all sensors as well... Any codes showing?
    – Solar Mike
    Commented Nov 6, 2017 at 5:22
  • electronic throttle? did you do a throttle relearn? is there any scan data you can show us?
    – Ben
    Commented Nov 7, 2017 at 2:17
  • 2
    To clarify: where did you put the silicone? Surely not on the head or gasket??
    – 3Dave
    Commented Apr 6, 2018 at 1:48
  • For a brief moment I actually thought the car was actually called Taco..
    – Paramone
    Commented Oct 3, 2018 at 8:30

1 Answer 1


The obvious thing to check in case of hunting idle here is unmetered air or a vacuum leak.

A quick (not comprehensive) checklist:

  • Are all intake-side hoses connected?

    Possible suspects: brake booster vacuum line, crankcase ventilation line, EGR line...

  • Is the idle air control valve functioning as it should?

  • Are there signs of an obvious leak?

    If it's bad enough, there should be an audible hissing sound around the engine

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