Replacement engine went into Limp Mode

This is possible that it is something like this but that sounds more like an electrical issue.

Did the vehicle drive normally after this, or did it stay in limp mode?

https://www.2carpros.com/articles/reduced-power-limp-mode

I would suggest we start from the beginning and check the codes and the state of charge on the battery.

Here are two guides that will help with this:

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

https://www.2carpros.com/articles/car-battery-load-test

If the battery is low on charge, then the vehicle will have all sorts of different issues so we need to start with this or we will be running in circles trying to figure it out if it is something like a drained battery.

Thanks

It didn't drive at all after that. The battery is new, but the car won't start at all. If I unhook the battery for about a day, then hook it back up it will start up and run for a few seconds then shut off again. It won't crank again after that.

Okay. If this is the case, then is the theft light remaining on? Did they swap the engine with a brand-new engine or a used engine? Any chance they changed the PCM as well?

If the theft light is on or flashing, then we have an active theft issue.

Disconnecting the battery and it starts then stalls is typical of a theft issue, so we need to start with start with this info.

https://www.2carpros.com/articles/how-to-reset-a-security-system

If we are not able to disable the system, then we need to check for any codes using a code reader that can pull what are called body codes.

Some are not able to pull these, so we need to double check that.

Let me know about this and we can go from there. Thanks

It was a used motor. The security light is flashing while the key is off.

Okay. Does it stay on or flash when you turn the key to the on position?

Just turn it to the on position without starting the vehicle and see if the theft light goes from on solid to off completely.

If not, then we have a theft issue.

When the key is in the "on" position it goes off completely.

Okay. This means the theft system is turning off so that is a good thing.

Next thing to check is the fuel pressure. I am not sure why it will start if the battery is unhooked but we need to just start crossing more things off the list and a start and stall is also caused by a fuel pressure issue.

Here is a guide that will help with this:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

I attached the process from the manual that will give the detail needed. Let us know what you find with this, and we can determine next steps.

Thanks

It won't start while the battery is unhooked. Since it stalled after leaving the shop, it won't crank at all. But if we unhook the battery for about a day then hook it back up, the car will start for a few seconds then shuts off again and won't crank back up.

Okay. I think we are not using the same terms. When you say it "won't crank at all," do you mean that the engine will not turn at all when the key is turned? Meaning you try to start the engine and it will not turn over at all? Or do you mean it will turn but the engine will not fire and run?

Maybe if you can go out and turn the key while getting a video of it that will get us on the same page.

Because if you disconnect the battery and then the engine starts and stalls but will not crank again then that is a very odd issue.

However, I suspect you are using the word crank meaning it will not start but it will turn over just not start.

Basically, we need to know if after the engine starts and stalls, is it a no crank no start, or a crank no start?

Thanks

Crank, no start.

Okay. That is good. So that means we need to cross off the things that we need in order to start the engine.

You need air, fuel, spark, and compression. The fact that it starts after you let it sits sounds like a theft issue but if the light is off when you turn the key on then we need to move onto these items.

So, compression is not the issue, or it would not start at all. Air is most likely fine as well. So, we need to find out if we don't have fuel or spark.

Fuel pressure is more likely, so we need to follow the info above to check the fuel pressure and go from there.