I was recently gifted a 1990 Civic SI that was my nana's for 30+ years. She took good care of it but it has been sitting for a few years and needs some love. I've been doing a lot of research trying to troubleshoot and figure things out. It's my first car so everything is a learning curve. The maintenance manual has been a solid guide but comes up short. I've been seeing some super helpful threads so I thought I would join in order to comment, ask questions, and hopefully be able to one day help others with the same problems.

My primary concern is that the car won't start when the engine is already warmed up (after a stall, or if it is turned off and then back on again). Current theory is that it might be the temperature control sensor or electronic air control valve, but I just realized I have a mystery coolant leak so I might need to deal with that first lol. If I can get the car to drive then I'll deal with the leak(s) and cosmetic things.

So far I have replaced the battery and fuel filter. In preparing to replace the temperature control sensor I noticed the coolant reservoir was empty – filled it back up and ran the car for a bit, there were no apparent leaks under the car. 2 hours later the reservoir has lost half of the coolant. Again, nothing leaking under the car. My uncle replaced the upper hose from the rad to engine a few years ago, perhaps the lower hose has gone? Might try jacking up the car and looking under the engine belly pan. All suggestions to any of these issues are welcome.

Cheers!