Pontiac Repair: 2004 sunfire, needle in a haystack, coil assembly

Question
QUESTION: i have a 2004 sunfire, no cruise, 2.2 ecotec that has a wild idle and surging problem with some stalling.  have a new map sensor, tune up and have tried a new set of coils with with icm.  problem still persists with wild surging when hot or cold 1000 to 3500 rpm and a hard downshift to first when this occurs, when shutting engine off while driving, auto transm, it sometimes resets and sometimes doesn't

ANSWER: Hi Doug:

has any service engine soon lamp come on? If so there will be a code(s) stored in the engine computer and that would be a clue as to where to start looking. It couls have a bad engine sensor like a Throttle sensor. Did you replace the MAP senaor with an O.E.M part or aftermarket? where the part put on this chasing this issue or did it crop up after you changed the parts? Same with the ignition coil assembly O.E.M part? I doesn't matter what brand car you are working on Always use O.E.M. parts from the manufacture that built the car because you just asking for trouble.


---------- FOLLOW-UP ----------

QUESTION: Todd, thanks for getting back to me, I failed to mention that the car has thrown codes for high idle and misfire numerous times.  As for the map sensor it is oem as is the ignition coil assembly.  It seems that this is a needle in a haystack situation and I wonder how I can check for a vaccuum problem.  Any further advice would be greatly appreciated.  Thanks again, Doug

Answer
Does this car have a lot of miles on it? Is there any kind of rattle engine noise when it's running? Does it ever run smooth or does the idle constantly race? I'm thinking is it never idles down and there is any kind of engine nise that possably that the timing chain may have jumped time. If it runs smoothly at times at a normal idle spped then that is not the case. This is going to be a hard one to fix with out the air of a scan tool to see what all the engine data is showing It's impossable to tell you what's going on. When the engein does run smooth it that ever happens you can put a vacuum gauge on it and that engine at idle should have around 15-18 inches of vacuum. much less then that and that could be the issue. you could have a vacuum leak and a hose or the intake manifold gasket could be leaking between the manifold and the head??