Did a Head gasket on my car along with new timing belt and all new fluids. After doing so we started the car back up was running good so took it for a test run, everything was perfect until i came to a stop and noticed the idle was like skipping a beat but it was not consistent randomly it would do a little cough and the needle would just shake not really rise in rpm but just bounce in place. check engine light came and and dont remember the code but do recall it saying something with the camshaft and being (over retarded) we opened the hood again and double checked chain and timing belt. also checked all plugs. Second time firing it up it said miss fire but that went away after a long idle. but it still has this random rough idle and can not figure out what else is causing it. I dont know to much about cars under the hood but have family who own a shop and i am just trying some sites here to see if any one else has had this problem so i know what else to try. We have a lot of hours building up under this hood. another this is i heard a small hissing leak behind the head of the engine but cant see where that is coming from. Any help would be great thanks.

 

Never had this problem myself but sounds like an intake tract like to me. Make sure all hoses are sealed and connected properly. also, make sure all plastic parts aren't cracked.

Good luck