I recently bought a used 1994 civic vx with 220,000 miles on it. Since then I've driven about 200 miles. This is the best description I can give of the problem:

In first, second, neutral, and when the engine is cool, the engine runs fine (as far as I can tell.) In third gear and up after I've been driving about ten minutes, the engine seems to ignore throttles less than 50%. I read up on how the vtec-e does special things at low rpms, so my guess would be that the economy mode just buggers off when the car warms up.

For example: I'm coasting at 35 m/h in third gear. The engine is idling fine. I press down the pedal. The engine revs up just a little bit, then returns to idling (I think; It idles quieter than the frame.). The car slows down as it would if I was not pressing the gas pedal, as I continue to push the gas pedal. At around halfway down, the engine sputters and begins to run and sound as it does in second at higher rpm while the car accelerates quickly.

So my question is "What might break that would cause this?"

 

Have you checked for ECU codes? The "check engine" light bulb is often removed from used cars to make a quick sale. The light should come on and then go out when you turn the key on but don't start.

The VX needs to have the proper (expensive) wide-band O2 sensor to run properly. This is assuming you still have the VX engine. Civic engines and parts are easily swapped around.

 

I know that the engine block, at least, is a D15Z1.
The CEL works, and when I jump the service connector it gives no codes.

Could it still be the O2 sensor? How can I be sure that it's bad before buying a new one?

 

i had the same problems with a vx i owned in the past. no cels, but it turned out to be the o2 sensor. they are not cheap unfortunately.

 

I bought the car for $1500. I expected to have to spend a bit on repairs.