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I am getting cylinder misfire OBDII error codes after performing a cylinder leakdown test. During the test, I was turning the crankshaft to reach TDC for each cylinder and I'm now thinking whether it needed to be readjusted again (to a startup position) in order for the firing to run. The engine is on and running but slightly shaking and the check engine light is on (which is why I got the code readings). Or could moisture (it was mildly raining) have affected the connection between the ignition coils and the spark plugs?

Toyota Tacoma V6 2007.

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    Double check to ensure your firing order is correct. It's easy to get a couple of spark plug wires mixed up. – Pᴀᴜʟsᴛᴇʀ2 May 6 '16 at 23:56
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    Check the spark plug and plug wire on the cylinder that is misfiring. – Moab May 7 '16 at 1:43
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    Please post the make model, engine and year of the vehicle. – Moab May 7 '16 at 1:44
  • Paulster, that has been ruled out for sure – amphibient May 7 '16 at 5:40
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    I'm not sure I see the connection between a leak down and a misfire. Seems disconnected to me. – DucatiKiller May 7 '16 at 8:56
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You don't say why you needed a leakdown test in the first place. If you rotated the engine by hand in the opposite direction that it normally runs and it has a timing belt then it is possible that the valve timing may have jumped. You would have to remove part of the covers and check that all cam timing markes line up as per the manufacturers specs. If its a long way out you could have a bent valve as a result. Before that check that one of your HT leads isn't damaged from removing it. Test with an ohmmeter for an open circuit. As said before check the firing order. Short out one HT lead at a time to determine which cylinder is affected, then try swapping leads if the affected cylinder changes then the lead must be faulty.

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Presumably you removed the sparking plugs to perform the test and have likely disturbed one of the connectors or possibly haven't got one of the plugs at the correct torque.

One thing I've seen in the past was someone remove a plug, accidentally drop it then refit it. This caused a misfire because when it hit the ground, the electrode gap closed up.

Remove your plugs, check the gaps, refit them to the correct torque and make sure all of the wiring to the plugs and associated coil(s) are firmly and correctly connected.

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