Hi guys! New to the forums, I only ever planned on reading forums rather than posting, but my 8 is having some huge issues and I have no clue what to do.

Starting from the top, I got this car running with a (new to the car, lightly used) Renesis motor about a month ago. It is in the 90's psi on all faces of both rotors. It has been running like a trooper (although struggles to start hot, figured it was ignition, have new ignition system on the way), up until a few days ago. The first symptom was that the dash gauges would suddenly turn off. At first it was only the middle and right gauges. This was the only issue I had with the car that day (It had been having issues with a wacky speedo in the past, but few and far between). On the gravel road back to my house that day, the gauges turned back on, and the car misfired one time.

The next day, I went to take it on a 10 minute commute to work. I tried to start the car and it cranked cranked cranked, wouldn't start. Stopped turning the key. Turned the key again, the car immediately fired up. Thought it was weird but took it down the driveway to the highway. At this point I realized the car had zero power steering, and zero gauges were working. Disregarded and began accelerating on the highway. The car then started misfiring BAD. As in every ten seconds, boom misfire. Of course I immediately limped it home and turned the car off. (In the month leading up to this, the car has taken hour long trips, been driven 400 miles, and has not misfired ever)

The day after, I went out to go find out the issue. Checked my spark plug lines and such, I was worried one may not be plugged in all the way since we had just taken them off to comp test the car the week prior. All seemed well. In fear of a bad connection, I tightened the battery connections. Turned the car on, fired right up. Drove it around a little, mysterious misfire seemingly disappeared. Still no power steering or gauges. Once again on the gravel road my gauges came back to life and my power steering returned. As quickly as they came back they disappeared again. Went to take the car on the highway, was accelerating pretty slowly just fine, as I went to shift into 4th gear the car misfired again. Took it on a 10 minute trip and it did not misfire after that. Gauges and Power steering did not work unless I hit a bump in the road.

I then read the codes. I was shocked to find TWENTY different codes. A code for every single module. I'm freaking out now as something is clearly very very wrong. The car had only had two codes prior to this, which were for the rear O2 sensor due to my CAT delete.

Two of the more concerning codes - (There are a lot)
-U0073
-u2516-ff

So I pop the hood expecting something is loose. Rooted around the engine bay with no luck finding anything clearly wrong. Turned the car on (fired up first crank) and began messing with things. When I touched the wires that connect to the plugs that connect directly to the ECU, things went very sideways very quickly. Touched the 1st plug, my gauges and power steering came back. Touched the second plug, the gauges and power steering went away again. Touched the third plug... the car revved itself way up to 3k rpm, erratically revved up and down. then killed itself completely. I turned the car back on, the idle is now very rough.Touched (I'm talking LIGHT touch) the plug again. Exact same thing happened again.

I am now stuck on what to do next. The plugs connecting to the ECU are not loose at all. I am confused as to why the car is suddenly doing this after 400 miles being driven, as absolutely nothing has been changed. I don't even have the first idea as to what to do to even begin to fix this issue. Any help or potential solutions are GREATLY appreciated. Really want my car back!!

 

It's possible the ECU terminals solder has cracked and while the plug is fully inserted, inside the ECU they're barely making contact and vibration causes them to randomly lose connection. You could remove the ECU and check for movement of the terminals? Or open the ECU to examine visually. That's all I can think of that would connect affect all 3 plugs at the same time. Another less likely option is the system voltage is too high because the voltage regulator has failed and the electronics are losing their mind. Easy to check with a voltmeter while the car is running.

 

Thank you so much!!! Will definitely take the ECU apart tonight and check it out

 

Update:

We’ve inspected the ECU now, no broken terminals, threw a different ECU in and are facing the same issues. Voltage was 14.6. The old ECU had some rust in it when we cracked it open, but the new ECU is basically pristine. Took it on a drive with the new ECU, same issues, but now the gauges just won’t come on at all, same with power steering. Continuing with the severe misfire as well

 

As per the video attached, the car also will not even try to start. The starter relay is clicking and that’s all that happens

 

You cant change ECU without reprogramming the immobilizer. In the video, your gauges arent dimming when you turn the key, so I suspect its immobilized. Bottom right of the cluster is the security light. Looks like everything is lit.

Is that 14.6V while the car is running or engine off? Its on the very high end of acceptable if the engine is on. Overcharged if at rest.

It sounds like electrical issues obviously so check and clean all grounds, especially ECU ground, make sure the charging system and battery are beaving correctly