I've also posted this same problem in the civic/del sol/el forum.

https://www.honda-acura.net/forums/s...d.php?t=199815


Ok, so heres the rundown.
-1992 Honda Civic DX sedan w/ D16Z6 swap
-Been running p06 ecu on engine since November(lack of knoweledge of car vtec)
-Recently purchased ecu off of ebay---> http://cgi.ebay.com/ebaymotors/ws/eB...3AAAQ%3AUS%3A1
-Plugged up p28, check engine light pops up (uh oh)
-Drive on the p28 for about 20-25 mins
-Before exiting car, I notice heat meter is on the H!!!
-Plug p06 back up, car runs fine(no vtec) but no overheating problems
-CEL check reads code 21 (vtec spool solenoid valve) [attached thumbnails]
-Need plug for solenoid, and wire to ecu for working vtec
-But the question remains...Why did my car overheat???


Why?

Thumbnails may or may not help.