let's start from the very beginning. about half year ago, my check engine light came on and stayed on for no apparent reason. i took it to my mechanic and he told me it's a faulty oxygen sensor. the car drove fine with the lights on, so didn't have it replace (i know, i know, but now is not the time for lectures). about 5 weeks ago, i cannot start the car one cool afternoon, i turned the key but no clicking sound at all. the car finally started after i turned the key and hold it down while stepping on the gas padel for about one minute. i drove it for about 170 miles straight and turned the engine off. i tried to restart the engine right away and it hesitated alittle and it made a high pitch grinding noise for about 2 second before it started again. after that no problem starting it for about couple weeks. had my battery and alternater checked- both ok. also had my mechanic take a look of the flywheel as was suggested on this forum- he said it was fine also (i still wonder if he actually looked). lately, the car have some problem starting (worst when engine is hot)- the engine will start and rpm shoot up to about 15k and dip right down to about 500 (it died twice) and bounce right up again.
finally changed my oxygen myself two weeks ago and disconnected the battery for about an hour and reconnected it- voila, check engine light is gone!! however rpm dipping at starting persisted. this past saturday, a very very hot day, i started the car and the rpm dipped as usual (the only difference is that this time the air condition is on auto and full blast at start up) and the car start to vibrate slightly as i pull out the parking lot. as i started driving down the road, the engine persisted to vibrate/quiver only slightly. as i pull to a stop or when the rpm dipped too low, the engine started to rock/vibrate violently and check engine light came on again. i pulled over and turned off the enging after about 3 min of driving. the car restarted fine (with the usual dip in rpm of course). what's going on with my car??!!??!!??!!?? please help.
sorry about this awfully long post. i want to tell the the whole truth and nothing but the truth
i am going to change the infamous ovp relay this weekend and see if that helps.