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Hello,
I have a 1996 civic hatchback with a jdm b16 engine in it, the car will turn on for cold start and run normal but as soon as the car warms to temp the idle will sit at about 600rpm and not change (feels low). When driving the car it will randomly start to bog down for a couple seconds and then come back constantly. This happens more with city driving than highway, there is no check engine light on. If you let it sit there and press the throttle it's as if there is a vacuum leak revving up and down, release the throttle and it goes down to 600 and stays there.

I have another ek with 96 type r in it and I have swapped the IACV, TPS, MAP, ECU, Distributor, wires from it and still no change. I replaced the fuel pump, filter, regulator, dropped all the fuel and replaced it and still no change. I replaced the timing belt, water pump and tensioner and the car ran worse, the reason for doing this is the previous pump was leaking. I have checked timing about 10 times and all the marks are lined up, set ignition timing and still the issue is there. Sprayed starting fluid all over the intake, tb for leaks and nothing. Did compression test and 1-210, 2-185, 3-197, 4-205. Then performed a vacuum test and it would stay between 18-19inHg at idle and raise to 21-22 with throttle.

I feel there is something physically wrong versus electrically wrong since there is no codes and swapping sensors and ecu's made no change, I have been leaning towards there possibly being a valve issue but not 100% if any body has some insight or guidance please let me know. I have attached some videos of the issue.