possible overheat/stumbling issue at idle

Z_ealot

Hey everyone,

so as the title of the thread suggests I may possibly have an overheating issue. I've had overheating issues in the past and had them taken care of by changing out a bad thermostat, however, recently I changed out the spark plugs on the car with a fresh batch of OEM denso spark plugs after having a set of NGK spark plugs go out on me prematurely due to a parts store and NGK having the wrong spark plugs listed for the 370Z. car ran great after I switched out to the oem denso...fast forward to a few days after I installed the correct spark plugs and im starting to get an intermittent stumble of the engine RPM's at idle, checked what the engine was up to through a scan tool I have and discover that the short term fuel trims are hanging at or close to 25% for a good 30 seconds and then the engine stumbles and the fuel trims correct themselves back down to near 0%. thinking that maybe it was just the engine clearing itself of some carbon buildup from having the wrong spark plugs in it I drive around for a few miles after this and everything is working fine. next day which was yesterday with temps around 80 degrees outside I decide to turn on the AC and just happened to have my scan tool opened up on my phone to keep an eye on things. oil temps were around 200 and had just gotten off the freeway and parked to go visit a friend and sat there a few minutes to watch what the car would do. next thing I know im seeing coolant temps start to climb over the 220 mark with no sign of the oil temps dropping despite the radiator fans being on full blast. shut the AC off, radiator fans still going and coolant temps start dropping off back to normal and drop even further after I open the hood of the car. so my question is this....does anybody have any idea what the heck is going on?