Hi everyone,

Recently rebuilt the engine according to stock specifications, following the manual's recommendations, including valve clearance adjustments. Compression tests indicate good results across all cylinders.
However, upon installing the engine, I discovered that cylinders #4 and #6 are dead, accompanied by a persistent banging noise in the exhaust.

Troubleshooting Steps Taken:

• Replaced the cam sensor and VVTi solenoid
• Swapped out the ECU (found a cheaper replacement).
• Conducted a noid light test on all injector connectors, and all seemed fine.
• Replaced all the spark plugs then started swapping around coil packs and injectors between functioning cylinders and the dead ones (#4 and #6), and still no difference, same dead misfire in the same cylinders (#4 and #6).
• All coil packs and injector connectors are in the right order.

Lifting the coil packs from cylinders #4 and #6 didn't change the engine's behavior, whereas lifting any other coil pack did. However, disconnecting both connectors from injectors #4 and #6 completely stops the banging noise without any other change in the engine behavior, suggesting that when all the six injectors are connected, fuel from cylinders #4 and #6 is being expelled unburned into the exhaust, resulting in explosions within the exhaust pipe.

Current Hypothesis:
Given that air, fuel, pressure, and spark are all present, but combustion is not occurring, the issue likely stems from timing – either spark timing or injection timing.
Now, I'm honing in on the crank sensor as the last potential culprit. Even though I tested its resistance which falls within the manual's specifications, it remains under suspicion.

I'm at a loss here and would deeply appreciate any insights, suggestions, or experiences you may have had with similar issues.

 

What were the compression test results for each cylinder?

 

Close to 190 psi for all cylinders

 

Do you have the ability to 'scope and graph the crank sensor? Would be very helpful to see the waveform.

 

No, I have no access to that.
Forgot to mention that I've intermittently encountered a few error codes, primarily:
P0300: Random misfire
P0304: Cylinder 4 misfire
P0306: Cylinder 6 misfire
I've also observed misfire codes on other cylinders on rare occasions.

 

Without the ability to see waveforms you're left firing the parts canon.
forgot to address this. Did you use a Toyota part? Why didn't you replace both.

 

Replaced both, the solenoid is Toyota OEM, cam sensor is from a Chinese brand

 

Yes sir, flying blind without a scope.

Question for OP, is your noid light incandescent or led?

If using an led test light you may see pulses on the trigger wire at the connector for coil packs.

Do you have the pin out for the coil pack or do you need it?

 

Put the original cam sensor back in, swapping in cheap parts could introduce another variable.