Civic EG

alright so i have a ej1 with a b16a and it was running on a p28 with a chip for a b16a2. (its all obd1 by the way) and it was idling a little high, and it was also not going that well running wise. so i put in a p30 and it is idling very different. it idles high like normal during warm up and then goes from 800- 1350 rpms and back continuously while in neutral or with the clutch in. i cleaned the iacv and no change. i even checked to see if all the vacuum lines and have not been able to locate one that is not on so i am clueless on what to do now? any suggestions.

Any codes?

Check your O2 sensor and your coolant level. (Low coolant MAY cause idle issues.. it did for me at one point)

Also, it may be your TPS or MAP sensor that is faulty. Start by changing things one by one, and you will sure to find out what's causing the issue.