MAP sensor question

[gregk2659]

Aveo runs rough after starting up and at idle it sounds like it has almost a miss at times,this is after a head replaced due to timing belt failure,all sensors are new and it runs ok while on road but idle sounds wrong,once in a whilee MAP failure code turns on check engine light,is there anything else other than map sensor that can trigger this,its already been changed,has new cam sensor,injectors,idle air control,plugs wires.with a vacuum gauge at idle it has 12 inches,and has a small variation at times,any ideas what could cause this,it runs rough till it warms up

[avguy]

What year/mileage? Was the engine running fine before the belt broke? If so, did you do a compression/leak down test after the head was replaced? If not, I think you want to make sure the engine is ok now before putting more $ into it.

[gregk2659]

its a 2005,ran fine before belt broke,compression good after head assembled,its almost like a vac leak but cant find anything,engine has 70 k

[avguy]

If it were mine, I would be suspecting something about my repair job to be the cause, until proven innocent. I'm sure you were careful, BUT is there any chance the timiing is off by maybe one notch on one of the pullys? Having done this job a few times, it's not hard to imagine how this could happen. And having to find TDC first adds yet another chance to go wrong. I've never had one be off a notch, and don't know exactly how it would run if it was off. I wonder if the loop closing after warm-up might be compensating for the misfire by adjusting the gas based on the full sensor input.

[gregk2659]

i have already made the mistake of timing belt 1 tooth off and corrected it,even when warmed up idle has a mis once in a while and i havent found the culprit yet,thanks for the reply and ill keep at it