Key On - Engine Off causing Injectors + Plugs to fire

Where to begin on this one..... calling some much needed help from the IGN/Wiring gurus.

Synopsis: Key On Engine Off scenario, causes Injectors to Fire sequentially, and Spark plugs to fire.

Vehicle Info: 2004 Tacoma, 3.4l, Auto, 240k, well maintained, no aftermarket wiring tapped into factory wiring, no indications of mice or other wire chewing. No previous wire repairs.

Summary: Been fighting this for quite sometime, 1yr plus. Originally thought the issue was due to the factory oem injectors with 240k miles were leaking as proven via other threads on this topic.
After replacing Injectors, among other things (will get to that in a second), stumbled onto the fact that the Injectors were sequentially firing, and spark plugs firing. Hooked up a scanner and was actually able to scan 114 engine rpms and Ignition timing being advanced. COR being removed stops the fuel pump, but nothing else changes.

With 240k miles and original owner, I decided to replace a ton of parts just from wear and tear over the years, all started with a leaking valve cover. Again thinking this condition was being caused from old injectors leaking.

Parts all oem or Denso, nothing used: Plugs, Wires, ECT-i throttle body, Crank and Cam sensors, MAF, new tank, sending unit.
Purchased a good used ECM, replaced, same issue so can rule out an ECM unit malfunctioning.
Via a relay tester, relays all testing successful. Still need to set them on a meter to verify they are staying/open close fully.

Next thought is wiring.....ordered a used harness and ignition module to help with troubleshooting. My thought is that the Cam and Crank sensor share a ground located somewhere in the harness that sits under the intake manifold. Still need to ohm those wires out to verify.

Found a thread that mimics that exact same issue, but never posted a resolution.

https://www.tacomaworld.com/threads/i’m-having-issues.794318/
Then specially post #23
https://www.tacomaworld.com/threads/i’m-having-issues.794318/page-2#post-28471972


Welcome any other thoughts/ideas troubleshooting.

 

That's very interesting, only time I've ever seen fhis was on a Dodge 3.7/4.7 with a failing cam sensor.

Does it show RPM when it's doing this?

 

It's an odd one for sure. Registers on an OBD autel scanner but not enough rpm to show on the cluster.

 

So the RPM value in scan data isn't 0?

If that's the case my next step would be to put an oscilloscope on the cam and crank signal wires and see what's going on there.

 

Correct is doesnt not, jumps to 114rpm, and timing advances +5*

Need to get my hands on a oscilloscope....

 

Fun update, issue has been resolved.
The High AMP alternator was producing a high level of EMI that was bleeding over to the CKP sensor causing a ghost RPM signal to the ECM to fire the Injectors/Spark.
Fix:
EMI wrap for the CKP wires 6" above the top of the alternator (right where it goes underneath the intake manifold. And then full wrapped down to the CKP sensor.
EMI had gone down but still required more effort. So used the lower alternator bolt (adjustable mount with/nut) to run a new ground from there to the frame. After this, all EMI is now gone and ghost RPMs are gone.