I pull off the cylinder and replace the head gasket with timing marks march up correctly on Nissan Qr20 30t. when i start the engine cold the rpm goes to 1500 and start to come back to 1200, and as the engine warms up, the rpm will rise back to 1500 when idling. I have change the MAF sensor but still the same. Kindly help with any advice. thanks

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    Welcome to Motor Vehicle Maintenance & Repair! Sounds like you might have a vacuum leak (this is a non-turbo engine, right?). Check all of your connections, to include vacuum and anything between the MAF to the head. Look for rubber pieces folded over where they connect to anything ... this has been a particular headache for me in the past. Mar 8 '19 at 16:12
  • Hi, thank you so much, I will check again as I have done that already. Mar 14 '19 at 8:38

Can find vac leaks by taking a propane torch not ignited jsut let the gas leak out and slowly move it around all the intake lines and parts, if you hear the idle increase you are onto something.

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