I got a 90 hatch with a 1.6L Vtech. At idle, after its warmed up, it has a rough idle varying rpm's from 500 to 900 or so. It has an intake, exhuast(no header) a DC Sports ECU. I'm not that experienced with fuel managment, haven't gotten that far in school yet, anyway, any help would be appreciated, thanks.

 

it might be the throttle body gasket

 

check for a vac leak.......bleed the coolant system, air in there can cause a rough idle. Sounds like a vac leak, see if all the hoses on the intake manifold are hooked up correctly

 

Get a bottle of carb cleaner and spray the engien wherever you think there is a vac leak. If there is a vac leak then the carb cleaner will get sucked in the engine and you should be able to see the carb cleaner getting sucked in.

 

IACV, take it out, clean it out, see if that fixes your problem. I don't think it's a vac leak.

 

or you can check your map sensor.... did you not plug it all the way in... map sensor is located on top of the throttle body

 

Whats IACV?