I have a 1992 Civic VX with 315,000 miles. Ever since I bought the car it has had an issue with a very low idle that presents after the engine is warm. It feels like the engine is about to stall out (though it never has). I have done several full tune ups and run several bottles of injector cleaner through several tanks of gas. I have switched to 90 octane ethanol free gasoline and none of these things have resolved the idle.

I was thinking there could be a vacuum leak. When I bought the car the previous owner had changed the timing belt (himself, he claimed to be quite the honda tuner). The upper timing cover was missing and there was a steady leak of oil coming from somewhere around the head, but it wasn't burning any oil and there was no sign of coolant in the oil...so I was pretty sure it wasn't the head gasket. I have changed the valve cover seals and installed the upper timing cover and the oil leak was cleared up.

I also changed the MAP and O2 sensors...still a low idle.

I am still suspecting one or more dirty fuel injectors...but at this point, I am pretty much stumped.

Any ideas?

 

The low idle is by design. Should be right around 450-500rpm as part of the fuel saving strategy.

 

Once the motor heats up it isn’t even hitting 200 rpm at idle. Like I said the motor shutters like it’s beginning to stall but never does.