bignosewhipper

1991 Civic STD
Short Block - d15b1
A6 Head
p32 intake/TB
pm6
MONOTech Harness

So I did an MPFI swap recently and am now at the point of not getting any CEL codes when everything is hooked up. The problem I am having is the surging idle issue. RPM's from 1500 - 2000 and it keeps bouncing.

What I have done:
-cleared any air bubbles in coolant system, twice.
-checked all vacuum lines with carb cleaner, no leaks
-checked all intake bolts on intake manifold, all torqued and installed properly
-Replaced IACV (albiet with a used IACV but guaranteed)

Every time I plug the TOP air hole in the throttle body (IACV) the surging stops and the idle goes back to normal ~750 rpm and no issue. Power is awesome, and everything works well with no CEL.

This lead me to think it was the IACV so I bought one off of ebay and installed it. It didn't change a thing and the surging continues, however, when I plug the hole again, the car works as it should. I have taken the IACV out and cleaned it with carb cleaner, let it dry, and re-installed. I get the same Surging issue but no CEL.

Now, when I unplug the IACV from the harness, and start the car, it throws a CEL 14, which is what it should do, but the surging stops and the car works but with a little hesitation. When I plug the sensor back in, CEL goes away and the surging starts once again.

I know I'm close but can't for the life of me figure it out. I need some guidance.

Thanks in advance for your response.

bignosewhipper

Replaced IACV, surge still there, however it's a little softer than before.

Any ideas?

I have not re-learned the fuel relay yet, hoping thats it.

vxhbb16a

So what did you find out on this?