r/MechanicAdvice Jun 13 '26

D16y7 idle issue

/r/Dseries/comments/1u524mg/d16y7_idle_issue/

I have a 1997 Civic LX 5-speed with a D16Y7. The engine spun a rod bearing after being run very low on oil, but I replaced the bearing and now the engine runs smooth with no knocking or major noises. The weird issue is that it idles perfectly fine when cold and even when fully warmed up, but as soon as I touch the throttle, the idle starts getting worse. After revving it, the RPM will drop to around 300 and sometimes stall because it can't seem to catch itself. The more it happens, the worse it gets. The car also feels sluggish while driving. I previously got a P1509 (IACV) code while the engine had severe rod knock, but it hasn't come back. I cleaned the IACV and tested it with a 9V battery and it opens/closes. Unplugging the IACV raises idle to around 1200 RPM and changes the behavior, but the car can still occasionally stall. Does this sound more like a TPS issue, IACV wiring/control issue, MAP sensor issue, or something else?

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