surging?

[autox 89 dx]

I have a ZC SOHC with a Z6 head all the typ. bolt ons and it is converted over to ODB1 in a 91 Si, but it surges at stop lights and it just started doing it recently. It idols between 1500 to 400 RPMS. Every once and a while it will surge then stop and idol fine. What can this be?

 

[D16SiHatch]

could be a small vacuum leak, low on coolant, or could be a dirty iacv valve

***How-To Clean*** Your IACV a.k.a. Idle Air Control Valve - Honda-Tech

 

[autox 89 dx]

right on thanks