I just replace my brother headgasket on his 90 Civic Si. I started it up and it would run really rough almost as if it had a big cam in it, But really it was misfireing. It does a an FPR and I've messed with it, and the idle screw and it will idle fine when the screw is backed almost all the way out, and the fuel pressure is around 20 psi. This is weird, nothing has changed rather than .008'' of the head to true it up.

 

did you drop an injector on the floor? set the timing right (check that)?any CEL's.
the map sensor hooked up right?

 

map sensor is hooked up correctly, only one plug and vaccum line, timing is set to the left of the three lines... i have a crappy timing light that only flashes... not one with a dial. also injectors were never removed. all 4 cylinders are firing. I pulled each plug out and all are identical they are black and dry. First guess would be carbon fouled. so i took as much fuel away as possible but it doesnt run at higher speeds due to know fuel pressure. This is pretty much a stock d16a6. I/H/E new timing belt. water pump, headgasket, thermostat, no leaks, no over heating.

Also the EVAP system has been removed. for over a year, the purge solenoid is still intalled though, with a electrical plug, and two vaccum lines, one on top side and one on the bottom, the bottom one goes to the intake manifold on the back and the other isnt hooked to anything, could i completely remove this? I am about to go outside now and see if i can come up with something. I would greatly appreciate any ideas.

 

ok i went out, set timing to factory specs, cam timing is dead in with the crank, i have idle mixture screwed almost all the way out, just for it to idle right, idle speed is somewhere around, 500rpm and lower with lights on. fuel pressure is about 33-35psi at wot. took out for a test drive, and everything feels fine up aroud 2k-7k.... but from idle to 2k feels like the car is about to die. it is fairly low compression engine from the factory, but the head has been milled twice, i was contemplating with the idea that maybe we should bump up to 93 octane (premium) spark plugs are the stock replacements #6 heat range ngk's.
On the way home, I got a cel... #14 and #17 but when reading the codes it just did 14 short blinks, and same thing with 17 (17 short blinks)