-The first thing I did to my 90 4dr was to do a tune-up and get it running like it's supposed to.
-Do a compression check and if you're at the same around 90-150psi, you should be at least able to run for a time. Of course the higher the better considering..
-Get some good NGK plugs. JUst the standard V-groove, you don't need the high dollar crap.
-Pull the cap/rotor. Check for the red death.. If so, start looking for another good dizzy. Spray the inside with some GOOD silicone spray to water proof it and help with arcing. Take a little jewelers file and scrape off the electrical corrosion buildup on the rotor contact points and inside cap.
-Depending on your emissions location, you can find a header for less than 75.00 to your door. While your there, get a good 4-wire O2sensor and wire it up. I've noticed some minor improvements, but improvements none the less.
-And of course at least 2 1/4" pipe with some glasspacks. (remember, the engine is an air-pump. Free it up some)
-Flush the oil and use a few cans of seafoam or the like.
-For about 40.00 I got all the parts for a timing belt job (water pump, belt, seals cam/crank, belt tensioner) Then while getting 38+mpg I went to the local pull it and got a tegs 40/40 valve and master/booster. I already had the suspension from a 90 teg but for me the rear lower control arms didn't fit or the rear swaybar..?? SO I just went with the civ's lca's. (check the mileage of the donor car. If it's too high look for another, unless it's just too good of a deal. (I forgot my mileage on my parts and now have to replace wheel bearings)
-DO one end at a time so you don't get stuck not being able to drive it.
-Flush the brake system with GREEN rubbing alchohol, That way you can see when it starts turning green when you bleed it, it's getting all that crap out of the system. Spend the money and get a some GOOD dot-5 synthetic brake fluid (maybe Motul) Just don't drip it on your paint. And by the time it starts changing color back to golden color, it should be clean. (been doing that since I did it to a 1928 Packard Sedan back in the late 80's, never had a problem)
- Get some other seats.. I got rid of my crappy seats and fabbed in some 88 Prelude seats. Feels lots better with the adjustable side bolsters and the glides can be easily modded to fit. (you just feel better driving in comfy seats).
- I'd worry about the exterior last like they said. Well, unless you are upgrading the wheels. (i think you'd be happier with 16" rims at a max for clearance and geometry issues)
-Get a good printer if you don't have one already, extra ink and even a memory stick to save pics and other info of other cars either on this site or others of mods that you like.
I'm not really sorry for the long post. It's good info and wish someone told me stuff like this decades ago. Plus, I like the 4drs too
E