Hello everyone, this is my first post here.

I have a 97 accord 2.7 A/T with 247k miles that has a rough idle at low RPM's when engine is warm, idles around 700 RPM when warm with no accessories on in P/N. when in gear with accessories like lights and radio on the sputters like it's stalling and RPM's drop to the 400-500 range. sometimes it sputters while in P/N but not consistently. while driving the car does fine until warm, once warm the car starts sputtering at sop lights, hesitating on takeoff until approx. 1250-2000 rpm depending on load.

when the engine is starting up cold it works perfectly fine idling around 1200 and slowly dropping down as the engine warms up.

I have one CEL code for 02 sensor bank 1 sensor 2 heater element, and i've had this code since i bought the car. i have a scanner ad once the exhaust is warm the sensor starts reading and switching properly. since this sensor only monitors catalytic converter efficiency i have had no pans to change it.

this firs stated occurring on 10/17/14 at night and was acting like it was about to run out of gas.

this is really driving me crazy, so far i've spent 10+ hours looking into this with no luck.

earlier this year i had a similar problem, it was sputtering when cold during warm up and while in reverse after the car was warm. i changed he plugs with denso TT's , cleaned the IACV and the throttle body and problem was solved.

so far I've checked the IACV and it's still clean and operating properly, to test i started the car and held the throttle at 2000 RPM until it reached operating temperature and and let it idle on its own and unplugged the IACV, after unplugging it ran worse and eventually stalled out, i also tapped on it with the handle of a screw driver while it was sputtering, this had no effect.
i removed the TB and cleaned both sides of the butterfly and cleaned and adjusted the FITV to snug, bled the cooling system and checked the ETC using my scanner for proper operation. this made no difference.
i removed the EGR and inspected the ports, all passages clear and the diaphragm is working properly.
I have checked all spark plugs, they are all in god condition and look normal. no oil in wells.
inspected cap and rotor, both are in excellent condition.
inspected wires and tested for spark at plugs, distributor and coil. not missing a beat there.
listened to all injectors and all are firing without missing a beat.
watched the oscilloscope for the TPS,it has full range, upstream O2 sensor is switching properly, MAP is reading proportional, spark advance is averaging 16-18 at idle and is around 25 when accelerating and sputtering, higher when not sputtering.
i have checked for vacuum leaks, and have not found any.
so far i haven't found anything that isn't working properly/needs repaired/replaced.

i'm really stuck on this one guys, i'm thinking i'm going to need assistance from a veteran but any suggestions are appreciated.

 

the problem was sticking intake valves, i put a can of sea foam in the oil and drove it hard for 15 minutes and changed the oil while it was still hot then ran another can through the vacuum hose next to the map sensor while revving the engine around 2500 RPM. car is running smoothly now without hesitation. going to fill up the tank and put in a bottle of gum out in it for good measure.