I have a 94 dx with a vx D15z1 swap. Everything was swapped over, harness etc to run the egr and 5 wire o2. It would surge several times before catching a smooth idle when coming to a stop. So far I have:

-Replaced the iac, being this is a known issue (there is no fitv). The surging then got worse, and all the time.
-Bled the coolant system, no leaks or air in system.
-Sprayed intake manifold and all hose ports with brake clean to look for vacuum leak, none found.
-Swapped ecus with known good ecu.
-Found pcv valve bad, replaced and idled fine for 20 minutes. As soon as I tried to drive the car, it went back to surging again.

I'm not sure what else it could be, or where to start. Has anyone else had this issue?

 

Have you adjusted the base idle?

 

can you post a picture of the intake manifold?

 

Set the idle and ignition timing according to the procedure. Calibrate the TPS. Check the throttle cable tension.

 

I will try to post a pic later after work.

I have adjusted the idle with the idle screw, not at the throttle plate stopper. Would the tps need calibrated regardless, even if throttle position has not been messed with?

 

The surging isn't the problem, it's the symptom.

If your engine is idling too high, the ECU notices and cuts the injector PW. So the surging is literally your idle rising to the point where the ECU cuts fuel to the engine, then resumes once it reaches normal idle.

The most probable reason your idle is too high is because of a vacuum leak. If you want to learn more about the Idle control system in your vehicle, check out my thread; https://honda-tech.com/honda-civic-d...-read-3263995/

 

I've already looked for vacuum leak, spraying down the manifold with brake cleaner. Most hoses and all gaskets are new, engine was rebuilt before the swap.

Would tps calibration cause the surge?