MY 92 Accord EX with the 4 cyl engine has a tach that reads low only at idle, approximately 95% of the time. Occasionally it will read 600-800rpm with the auto trans in drive. I checked the connections inside the distributor cap, they are all clean and tight, as I know that the idle signal is pulled from the igniter inside teh distributor. I have owned lots of different Hondas/Acuras but this is the only one that showed this problem. By the way, I am pretty familiar with engine speeds, and even without a calibrated tach on hand, I know that the engine is idling pretty close to what it should be. The tach shows correct engine speeds above 1200 RPM, as the tach will jump up to this reading as sound as the engine picks up the slighest rpm. All RPM readings appear to be accurate above 1500 rpms all of the time. Its just at idle the the tach readings will drop below 500 rpm. the engine shows no sign of stalling, and accelarates properly from idle.

Does anyone have any ideas on how to fix this problem? Many thanks in advance! Great site!