Let me start off by saying that I'm as familiar with Hondas as the late ODB was with toothbrushes, so please forgive any lack of knowledge of these cars. I tried searching, but all the results for "idle problem" were related to hybrids or different engines.

Here's the situation:

My father bought a 1993 Civic DX that is completely stock. It idled irregularly (pulsating up and down) when we bought it, and we were told that the TPS was bad. Once we discovered that it was riveted on to the throttle body, we assumed that we had to replace the entire throttle body, which we got from a 77K-mile 1995 4-door Civic (probably an LX) from a boneyard. This caused a CEL and frequent stalling. We noticed that the junkyard throttle body had the MAP sensor mounted on it, while the original throttle body had a vacuum line in the exact same location. We drilled out the rivets on the original TPS and screwed a brand new (and supposedly tested and working) TPS on to the original throttle body, and now the TPS can be adjusted on the throttle body if the screws are loose. In one position, the car idles steadily at what we estimate to be 2500 RPM (this car has no tach). In the other position, the idle pulsates wildly.

My questions to the board are these:

What is going on?

How can I fix it?

I am thoroughly baffled by this car.

 

I've never had to mess with a TPS. From my experience with a pulsating idle it has been because of a vacuum leak. Sorry I couldn't help more.

 

exact same problem with mine, but i have a hybrid civic. turned out i had a bad wiring harness, and bad tps. and leak in the im

 

hey I had the same problem with my 93 civic and it was the sensor beneath the throttle body. if you take off the sensor i had a spring or something that had come lose and I just tightened it up and it never pulsated again. Try that hope it works for you.