Just swapped my blown engine with a low mile replacement on my 92' accord that I bought with a badly blown HG and almost seized motor. Just the long block was replaced, and everything on the old engine was working great prior to swapping it onto the new engine. Confirmed good compression in all holes after transfer.
Engine starts up initially when cold, and idles smooth. After a couple minutes, idle progressively get worse, & starts to stutter and hesitate. When held at high RPMs, it seems to clear slightly but RPM's on the tach show wild fluctuations that are not consistent with
The actual RPM's from the engine. When driven, will hardly stay running in drive or reverse when at a stop. I have really spent a lot on this car with this engine replacement, and am sweating having to bring it to a shop for diagnosis. Double checked no air leaks, cracked hoses, etc.

Trying to find the best start. Valve timing? Ignition system? (was working fine before swap)
New engine was supposedly just taken from a low mileage wreck, and was running perfectly, but I guess that doesn't guarantee anything...

Any help would be greatly appreciated.

. Replace ignitor and coil:

https://www.askmehelpdesk.com/cars-t...tml#post265896

. Replace Engine Coolant Temperature (ECT) Sensor, which affects fuel injector pulse width. It's located under the distributor. The ECT Sensor is a temperature dependent resistor (thermistor), whose resistance decreases as the engine coolant temperature increases. It provides a richer mixture when cold, leaner mixture when hot.

Thanks for the reply, I am going out to get a replacement and will give that a try and let you know any difference. If this makes no change, what would be your next direction?
Thanks again! I'm more then willing to work at diagnosing the problem, I just did not want
To be an admitted amateur throwing parts at it...

Fluctuating tach rpm definitely sounds like a bad ignitor, since the tachometer is connected to the BLU wire going to the ignitor inside the distributor. In other words, the ignitor drives the tach and fluctuations normally indicate the ICM is failing.