Crank no start after engine replacement

We are fixing and donating a '99 Solara for a family in need. We had a donor '99 that had a heck of a knock. Ran fine before the knock. We pulled the motor and dropped in a motor I believe was from an '01 (both are V6).

First attempt it fired but almost immediately cut off. It will fire every time and run for a split second and die. If you give it lots of pedal, you can keep it running but very poorly, sounds muffled, like a lean bog.

I used a NOID light to test if the fuel injectors are firing… have very intermittent light and not as bright as it should be. The coils are firing fine. We can keep it running with lots of throttle. The check engine light is flickering, not flashing, and the security light is intermittently flickering on and off. The RPM gauge also flickers at the same frequency and bounces between 0 and 300 RPMs, although the RPM is much higher.

Didn’t have my scanner with me at the time, but I am taking it back tonight.

I am leaning in the direction of a bad ground. It just looks and feels like a power supply or ground issue.

I have a lift and a shop just to play around with my car and work on my equipment, nowhere close to a pro. We are trying to help a family that really needs a car.

Any help would be appreciated.

Try MAF cleaner? Do you have a known good one from the two engines?

Is there a typo in your donor car date? If it really was out of a '91, that could explain why the '99 ECU won’t let it run right!

I bet you meant to type '01. :slight_smile:

Read the OBD codes to see what codes are stored and pending. That may help point you to the issue.

@Winslow
Yes, the car is a '99. The motor is an '01.

Update. Went today and plugged in a scanner. Car started up and ran like a dream. Put the hood on and wrapped everything up, then tried to start… same as last night.

Noticed the RPM was at 6K with the key on. Plugged in the scanner and it dropped to zero. Car starts and runs perfect with the scanner plugged in. If we unplug the scanner, it dies.

We jumped the CANBUS hi and low at the OBD2 and it runs great. Anyone have a CANBUS diagram of where it runs in the engine bay? Evidently, it’s something cut or disconnected in the engine bay harness.

Check the ground strap that is supposed to be connected to the back of the intake manifold.