I have a 1992 civic with the 1.5 D series. The engine is revving up and down continuosly, when the car is cold and after it is warmed up it still does this. I have checked the voltages from the TPS and the are within spec. I have also changed the PCV valve. The only way I can get the car to run normal is by doing the following: I removed the air intake, I saw two ports before the throttle plate that lead to the TPS. The lower whole is sucking a lot of air but when I plug it with my finger the car runs normal. If anyone has any ideas of why the car is doing this, please let me know, any info is helpful.