Hi, I just bought a 60k mile swapped 90' accord, used to own a 80' Accord just awhile ago.. Anyway, I decided to pick up this one for a decent price.. I noticed it has a hard cold start the next day (I'm assuming that's why he sold it) lol well with some research I found somebody had similar issues with the TW sensor which is one of the coolant temp sensors.. My accord takes a few tries of cranking with some backfiring and stumbling upon startup then suddenly runs & idles completely fine when warm the rest of the day. Further inspection, I found that maybe the person who did the engine swap did this with the wiring to that sensor and I'm wondering if this could possibly be my issue... Obviously looks like **** and I will be fixing it regardless haha.

Notice that black wire

 

Do you have any other issues when the car is running?

Definitely get that wiring in better shape. I'm not sure what engine and ecu were installed, but I'm not sure if that wiring is causing the hard start.

Your description sounds like a potential stop in fuel pressure at the rail and the car sits overnight. On your next cold start, turn the key to the II position, but don't try to start the car. The fuel pump will pressure the system while the check engine light does the bulb check for about 2 second. Listen carefully for the buzzing sound from the back seat. Turn the key off, and repeat this 2 more times. Then try to start your car.

If the car starts immediately, then the fuel pump check valve is suspect.

 

No other issues when the car is running, an engine from a 91' accord was swapped in. I let the car sit for a few days, turned the key a few times to let the fuel pump prime, and it did start up much easier. I put in more fuel and could notice a sweet smell coming from the gas tank indicating it's got some old fuel in the tank, but with more fuel it did start up easier on the next cold start.