When in neutral, my engine will rev itself up to anywhere from 1800 to 2300 RPMs then drop...only to repeat over and over again. I have no idea what it could be, but I'm only just learning about cars under the hood. I have a 93 accord lx sedan with a five speed manual.

 

Hi New Member..

If you have an AutoZone in your area, take your car there for a Free check up.
It has the sounds of maybe an air idle valve gone wrong..

Welcome to the HAF

 

The testing device won't do because the 93 Accord LX doesn't come with an external connection.

 

Have '92 and '93 prior. 5 spd's. >200,000 miles. Both did this/do this but only for a minute (literally) as they were/are warming up from a cold start.
Annoying, but not worth fixing in my book. If I idle them long enough warming up, the rpm oscillation doesn't occur.

Welcome.

 

The pre 96 to 90 Accords have a two pin service connector behind/under the glove box that will retrive any stored codes from the ECU or TCM.

Is this all of the time or only when the car/engine temp is cold or at normal op temp?

First answer, assuming no stored codes, a good cleaning if the IACV and FITV is in order, while there do the TB as well. You also want to be sure the coolant is full and no air in the system - do you have a coolant leak or done any work on the cooling system recently?. Next, you want to be sure the small coolant lines to the IACV are clear and not blocked off by old "crud".

 

They don't have the adapter for pre-'96 components. Haven't checked on the rest yet though.

 

I just went through this adventure myself. After you clean the valves listed above if that doesn't fix it then I recommend doing what I saw on an Eric the car guy video, Spray water around looking for an intake gasket leak or a vacuum hose. When you hit the leak, you should notice. The water doesn't hurt anything. Mine was an intake manifold gasket and it was interesting that when water got close you could hear the whistle like noise and the car would run better for a moment. Its fast and easy. Make sure you don't have any air in your radiator cooling lines as that will cause it too.

I cannot locate the video I saw Erik made but there is a similar one with scanner danner at this


Your Honda intake is easy to spray the stream right into the outside of the intake manifold where it meets the head. If its not leaking you will not see any change. Spray all the vaccum hoses.

 

It is not an adapter it is a two pin jumper (can be as simple as a bent wire) that you plug into the service connector under the glove box. You then need to look at the check engine light and count. For example one long blink followed by two short blinks means code 12. If there is more then one code it will go to the next code starting with a long blink first. If there are multiple codes let the light cycle through a few times to help ensure you have the correct codes written down.