Not updating the ECM
The modern automobile is a unique combination of electrical and mechanical systems all controlled by a computer. The vehicle’s ECM monitors performance, fuel/air mix and an incredibly long list of other things. If you fail to update the factory data in the ECM after the engine swap (before cranking the engine for the first time), you’re making a big mistake. It’s also called an ECU or PCM, but it amounts to the same thing, and it’s an important aspect of new engine installation.
What You Should Know about the ECM (Engine Control Module)
The ECM is responsible for controlling the engine, and it does this by using data programmed into it by the manufacturer and a host of different sensors in the engine and exhaust (oxygen sensor, camshaft position sensor, etc.). The problem here is that the engine isn’t the one it left the factory with, so some of the data is now inaccurate.
To compensate for the slight differences between the replacement engine and the stock engine, you’ll need to let the ECM “learn” the specs for the new engine. To do this, you’ll need to erase the adaptive memory for the unit, which isn’t as difficult as it might seem (the exact process varies from one vehicle type to another, though, so make sure you’re using the right method).
Once you’ve reset the adaptive memory, you can crank the engine and allow it to store the new data for the replacement engine once it reaches normal operating temperature. Generally, the first 50 warm-up cycles are accompanied by data collection. When looking for cheap engines, you always want to make sure all the components are in working order, which can be verified once a connection is made to a diagnostic computer.
Some ECMs are programmable by the mechanic through the OBDII connection. However, these are in the minority, and chances are good that the vehicle you’re working on is not equipped with one that accepts individual user-based input. Most programmable ECMs are aftermarket units, not OEM equipment. OEM units can be programmed to an extent by using an aftermarket computer with the right tables and data, though.
Alternatively, you can have the ECM “flashed” at an automaker-specific dealership. Dealers have higher-grade OBDII interface equipment and software with brand-specific software that allows them to tweak the data in the ECM directly through a handheld computer. Some of these systems are available for aftermarket shops, but be aware that some data on the ECM is proprietary and cannot be accessed by non-branded systems. This is important to remember during new engine installation.
