I've got a 93 Civic HB (D15B7), the issue is that, at idle, the rpm fluctuates between 300-1000 rpm. Also its lost a lot of power. When driving, the engine stumbles and pops (not quite back-firing). Any ideas or suggestions? :mad:

Replace the Ignition Control Module (igniter). Remember to apply silicone grease to the back of the igniter, before installation. Also, lightly coat the 4 male connectors on the igniter with silicone grease. Ensure connectors going to the igniter are tight. Removing the coil, before working on the igniter, gives you much needed room. If I were you, I would replace the coil and rotor, because of the age of your Civic and since you will have the distributor opened. Briefly "hit" the starter, in order to rotate the distributor shaft to be able to remove the screw securing the rotor.

Replace the Ignition Control Module (igniter). Remember to apply silicone grease to the back of the igniter, before installation. Also, lightly coat the 4 male connectors on the igniter with silicone grease. Ensure connectors going to the igniter are tight. Removing the coil, before working on the igniter, gives you much needed room. If I were you, I would go ahead and replace the coil and rotor, because of the age of your Civic and since you will have the distributor opened. Briefly "hit" the starter, in order to rotate the distributor shaft to be able to remove the screw securing the rotor.
If the ICM is failing, isn't that going to set off the check engine light?

Good question. My experience has been that they don't on pre-1996 ECMs; i.e. OBD-I computers. OBD-II computers tend to pick up almost anything that's wrong--almost to being a fault.

I was told by another, that it could be the IAC (idle-air-control), is there any chance of that?

Yes, the IAC is a logical component to suspect--so is the Fast Idle Thermo Valve. However, my experience is that the usual culprit is the igniter. None of those other items will affect loss of power and engine stumbling and popping (the igniter will).

So do you have any idea how much an ICM would cost, and is it going to harm my car if I drive it the way it is for the time being?

Here's what Advance Auto Parts charges:

http://www.partsamerica.com/ProductList.aspx?PartType=194&PTSet=A&SearchFor=Ignition%20Module%2FControl%20Unit

I'm running a G.P. Sorensen #11-5070 in my 1993 Civic DX. It came with a lifetime warranty.

Here's what RockAuto.com would charge:

TRU-TECH Part # LX615T {IGNITION MODULE}
2 Hole Mounting; Tec Ignition System
$55.79 $0.00 $55.79

It can't help things driving it in that condition.

Read section AA in the link below:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-honda-civics-46563-3.html#post260436

Keep me posted if this solves your problem.

Replaced the ICM and rotor and still no improvement, any other ideas?