Should I buy a spare ECU for my 1990 Si just in case? I see so many of these things for sale and people talk about them constantly. As far as I know, I've never had an issue with mine. I thought folks were just buying the ones they needed to do a swap, then selling the ones they didn't need after the swap. If I should buy one, then I guess I will need to test it in my car as soon as I get it, right? I get the impression there are a lot of different ECUs available, what do I need for my stock 1990 (49 state) Si? Is there a code number or a part number on my existing ECU that I can use to make sure I get the correct ECU for my car? Is the ECU I need a popular ECU, or is it one that should be relatively inexpensive because most folks are replacing it with something else and just want to get rid of the one I need? Are there preferred vendors for these things? What goes wrong with them and how would I know I had an ECU problem? Are they like the ICU, and you can just tell by looking at the circuit board, that it is in bad shape? Are they difficult to swap out? If I buy a spare how should I store it? Does it damage any other components when the ECU fails?

 

pull your ecu out and on the side it has the part #. that's the one you will want. But buy an extra just to have, not necessary. at least to me.

 

I probably wouldn't buy an extra. Post some good photos of the circuit board, we can see how the condition is. Usually capacitors need replaced. The price per capacitor is about $1 or so. They need soldered. It's pretty easy. Lots of people offer this service still. I'd probably have your ECU refurbed vs getting an extra that also needs capacitors. Capacitors have a shelf life, even if they aren't really used. The chemicals eventually just degrade. When they fail, they leak acid on the circuit board, making repair slightly less fun. These ECUs are so basic it's easy to repair broken/ate out traces. If you look at the top of a capacitor and it's starting to swell, there's your sign, it's starting to fail.

 

I second the opinion of buying a spare and get it refurbished with new capacitors. Then you can install it and test it to make sure it works against your working one in the car. However, if you ever plan on swapping the engine/exhaust/trans gearing/fuel type or doing any mods to the car that would require a modded fuel or ignition map, then both of your ecu s would be worthless. If you know yourself that well, and you plan to keep the car for 20 more years (and you think fuel quality will remain stable for that long), a second ecu on the shelf would be nice. As expressed above, they do go bad with time, so store it optimally! (Not above your fish tank or refrigerator).
Also keep in mind, Stand alone ecus have come a long way, and prices will keep falling as new units are designed. your ecu may go out in 10 years, and by that point a Link ecu will be cheaper than a replacement Honda unit (wishful thinking, maybe). That said, i have a spare ecu for my ef (obd1), but im still interested in open sorce stand alone ecus.

 

I "discovered" an ECU in my stash of parts. I need to catalog all the bits and pieces I have thrown in boxes. That might be my next project. It will probably require me start a thread where I can post a bunch of pictures and ask; "What is this?"