My poor old 92 Civic Si 16DZ6 sits outside and gets little drive time. Recently I have noticed that the idle is a bit rough, not surprising!

It pulls fine, but I also notice that the rev counter is reading 2000 rpm at idle though the idle speed is obviously lower, nearer 700 or so. when the engine is slightly revved it raises the rpm so its not stuck, when the engine is stopped it reads 0. No engine light.

Could the 2 be related? could a false rpm sensing cct cause the idle to drop a little? or is it just a but gummed up and the rpm reading a different problem.

Thanks
Terry

 

The signal to the tachometer comes from the igniter unit in the distributor. You either have a faulty igniter unit or a bad tachometer. Hook up a test tachometer to the connector under the hood to distinguish the two possibilities.

 

Well, I jiggled all the plugs and sockets in the engine bay, especially those around the Distributer and its seems OK now.. Wonder for how long!!