It seems that many people have had this problem with there cars within the past couple years since I have been searching for a solution for the past year or so. My engine would idle sparatically from 500 to 1200 rpms at times while sitting at a light or parked. I tried TPS sensors, IAC valve, Vac leaks. Everything that would have to do with the idle. Well I had gotten a tip from one guy that he had oil inside the opti. He replaced it and solved his problem. So I'm here to hopefully help a few people out if it is similar. I decided I'd head in and practically disasemble the entire front of the engine to get to the opti. Once removed, I notcied the bearing was shot. the rotor did not spin freely, it was binding up in all different spots. I take the cover off and the disc below the rotor was corroded and rusted. The sensor timing disc which spins inside the opti, also was somewhat corroded. I realized if this was the cause of the problem, it definetly needed to be replaced. I ordered a new one from Dal Slabaugh, good price. When I opened it up it spun perfect like a bearing should, no binding. Installed everything and have been driving the car for about a week now. Haven't had the idle surge, so I would definetly say the opti played a role in that problem. Also a cap and rotoe will do you no good, you need the entire distributor $$ but it comes with a new cap and rotor as well so that is good considering the cost of just those pieces.