Im getting loss of power, engine surging, sputtering, sort of jerking and rpm fluctuation. Happens around 35mph, I will depress the gas pedal and there is about 5 sec hesitation, , a deep throat sound, engine slowly picks up power and then surges and sputters...will pick up good power and all this wierdiness will stop after a bit. but happens occasionally. It seems to be worse on hot and humid days. Car has 70,000 miles. Spark plugs have never been changed yet. Additionally there are not any engine instrument warning or caution lights associated with this strange power loss. I have had the diagnostic computer attached while driving but it does not pick up any symptoms. Any suggestions anyone?