I've just purchased a honda civic, 1991 hatchback. After it warms up - the idle surges up and down - pretty drastically. I've experienced this in an '89 as well - so I'm wondering if it's a honda civic specific issue - and what might be causing it.

1. Check vacuum line connections.
2. Check each cylinder's compression.
3. Check for codes.
4. Check Idle Air Control Valve.
5. Check idle rpm and ignition timing.
6. Test/replace igniter.
7. Check ECM.