[Greenbuns]

I've swapped an f20b sir-t into a 98 manual honda prelude, I swapped all the sensors I need to run the factory Obd2a ecu/body harness as well as mated h22a TB to the f20b IM. At the start it was just a cel for my primary o2 sensor changed that hoping to solve the issue, the cel went away and the motor seems to idle a bit more steadier but not quite right. As of now when I start it it seems to climb to a rather high rpm of 2000 holding for 10 seconds until it starts bouncing from around 1300 to 2000 rpms until it warms up and seems to settle around 900rpms with a slight bog definite misfire, and once the motor reaches running temp it will idle so low sometimes it will stall, so I checked all my vacuum lines and connections using carb cleaner, cleaned out the iacv and the fitv. I also checked the timing because I had changed the belt while I swapped the crank sensors, but everything seemed to line up properly on cams and flywheel. Any ideas where I should check next? It did at one time throw a code for manifold absolute pressure but has never since that's why I checked the vacuum lines and tb with carb choke cleaner but didn't find any apparent leaks

 

[Auke -Willem]

Air in coolant system will also cause idle surge. Bleed air out properly. Should be a bleeding nipple near thermostat I think.
Otherwise sounds like some (wax) sensor thing.
No blinks on ECU otherwise If so, follow up on those.

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[Greenbuns]

Hello thanks for your quick response Auke.
I've just rebled the coolants system because after cleaning fitv and iacv I hadn't bled it again but still having the issue.
I tried pulling all the plugs all four were fouled black like its been running rich cleaned em all up and every spark plug and plug wire are working properly. So that leads me to believe the map sensor or tps is buggered?? Or could the injectors or anything else have anything to do with this?

 

[Auke -Willem]

Did you check if FITV inner screw is turned down all the way too Tends to come loose/up. Plugs shouldn't be an issue on idle surge normally.
Mostly, Vacuum leak, FITV or IACV, air in coolant. You checked all those. EGR cleaned as well

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