I have a 99 Civic SI that has a surging idle. Here are my mods: DC 4-2-1 header, Flowmaster exhaust, AEM Air intake, AEM fuel rail, B&M fpr and gauge, CTR cams, Edelbrock 65mm throttle body, AEBS Intake manifold. No ECU changes, no VAFC of any kind. The idle is surging, at a stop, from 1000-2000 rpm for 3 or 4 cycles, then surges from 1000-1500rpm for another 3 or 4 cycles then settles at 1100rpm. The throttle body and manifold were just recently installed, that is when the problem occurred. I checked for vacum leaks there were none, I then set the TPS at 4.5 volts because it was off. I have reset the computer numerous times and yet it still does it. I have a fairly new IACV on the car and doubt that it blew, but it could have huh. I also checked for leaks around the mass air, throttle body and manifold, nothing there. The only code that I am blowing is #14, to rich or to lean, I think I fixed that with a fuel pressure of 44 psi. I think I have checked for all leaks, but I might have missed something. Please help me if you can.

 

what sup man when u changed the intae manifold? did you pull a coolant line that was connected to the manifold? if so try bleeding the coolant system beacuase u might have air in the system.

 

We drained the coolant when we put the new manifold on, and took all coolant lines off. Here is what my boss says, he says it is because of the size of the throttle body, he has BBK 62mm on his B16A2 in his crx and doesn't have a problem, but I don't understand how the size could make it surge.