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I recently did a quick and dirty rebuild of the d16a6 in a '90 civic SI I picked up locally with a dead engine.

After getting it all back together, I found it wouldn't start- not even a cough. After diagnosing for a while, I found that if I held the throttle open a bit, it would start. Eventually I found that if I disconnect this part I'm about to link to, it starts and runs fine- minus a tuneup.

d9b8dce0.jpg?t=1329526185

So if that's connected, this car wont even cough. When its disconnected, it runs fine. It appears to be a little vacuum thing that CLOSES the throttle when it gets enough vacuum, which to me implies that the car is getting too much vac...?

Anyways, I'd love to know what it's called, and any ideas as to why its doing that are welcome...

thanks!

 
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dashpot diaphragm is what it is. Goes all the way back to the days of carburetors. Solution: adjust idle screw to prevent dashpot diaphragm from closing throttle all the way

 
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Very nice! Odd that it ran fine before the rebuild, but I guess since I cleaned all the valves and fixed some long standing compression issues, a lot has changed. I should adjust the valves, too. Thanks for the help!

 
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update:
Turns out there was a connector not properly plugged into the IAC valve. Once I hooked it up, I could re-connect this dashpot diaphram and all was well. Hope this helps someone someday!