I have a 99 civic with a d16y7 engine. Made this swap to the d16y8 intake manifold a few months ago, but there's only one problem: the idle still fluctuates up and down a little bit.

A few things to consider:

• I use the hondash bluetooth thingy to check all the parameters
• It's an automatic intake installed on a manual civic, which means that I had to block the holes on the back of the manifold
• When the car comes to a complete stop, the idle fluctuates a few times (3-4 times) going to 1500rpms and then back to 1000rpms
• I'm using the y7 throttle body, which has the IACV at the bottom
• IACV seems to be fine, running at a duty cycle of 3% when idling (it goes up to 20% when I rev then back to 3% when I stop revving)
• MAP sensor seems to be fine also, runs at 0.85v when idling (it goes up to 2.4v when I rev then back to 0.85v when I stop revving)
• TPS sensor is fine, stays at around 0.5v when idling
• Intake pressure sits around 285mBar
• Checked for gasket leaks and couldn't fine one
• All hoses are tight

Can someone help me please? I can attach a video later today

 

I had the same issue with mine. I needed to adjust the throttle cable, because it was holding the throttle blade open. With everything set right my throttle position reads about 9.5% at idle

 

Yeah I adjusted the idle screw and it got a little bit better, but still surges. Is the blade supposed to completely closed? Like all the way, because I tried that with a little bit of adjustment on the idle screw and it solved the problem, but the gas pedal was sticking so hard that I had to go back to how it was before (a little bit opened, which causes it to surge), and ended up not solving the problem.