I have a 93 hatch back with a h22a swap. When I start it the engine revs then stops the revs then stops, it does this until I have been driving for like 10 min or so. A buddy of mine said it could be the ECU. If any one can help I would appreciate it.

Thanks

 

is this only while at a stop or while driving too? it's kinda normal for your rpms to be a little weird at first with a cold start, and then go away. It could be normal, or if it seems abnormal to you it could be a dirty idle air control valve, that is if it's only doing it at idle.

 

Also check and clean the Fast Idle Valve:

 

If it has always done this since the swap, you may have some mis-matched parts.

 

I've had the car for about a month and it already had the swap. And it only does it while at idle.

 

Sounds like it's your IACV (idle air control valve) or your fast idle valve. Clean them both with carb cleaner and see what happens.