Cam position sensor is hall effect switch inside distributor. It will cause no symptoms aside from check engine light(E41), and perhaps a longer than normal crank to start time, as it determines synchronizes #1 injector for faster start. The typicallly start to fail as the weather starts to warm. The higher idle/stall may be because of the throttle switch that is integral to the isc motor. If it is seeing the throttle at rest when it is not, it will pull the shaft all the way in, as it is trying to control idle based on faulty information, and the result will be a stall. If it is not seeing the throttle at rest when it is, then it will think that a stall is about to occur, and extend the shaft, the result will be high idle. The TPS could be misadjusted, and/or idle relearn procedure may need to be performed. This condition may cause what is known as a sail-on, or the idle takes a bit of time to come down, but it should come down eventually. Often times the symptom for this is when, after acceleration and coasting, the vehicle will almost seem like it is accelerating. The rough run could be result of secondary ignition issues, or being a 1990, you are also in an era that saw alot of problems with shorting injectors, and that may explain the errant O2 readings.
Tuesday, April 12th, 2011 AT 3:22 PM
