i purchase a 91 civic dx sedan with d15b engine. before i had i tune up the engine light comes on after a while of driving of even just idling the engine for a minute or two. but if i turned off the engine the light also turned off *** soon as i turn on the ignition again. same story everytime i drive my car. and sometimed if i drive 55 stable the check engine light turns on. i did general tune up incuding the valve clearance is still the light turns on. and recieve my emission test and needed to be fix before june. any help would be really appriciated.