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I am reconditioning a 1987 A/T Z31 NA and have hit a wall and am looking for help. The current problem is that the engine seems to be misfiring and idling poorly. My dad and I have done a lot of work to it including valve/head work, new headers, new ignition coil, plug wires, valve cover and head gaskets, vacuum lines, new brake master cylinder, Thunderbird electric fan conversion, etc.

Running the car and switching to real-time diagnostic mode V doesn't show any errors. In mode III we get an error code for the cylinder head temperature sensor. We've used the factory service manual (FSM) to test the ignition coil, crank angle sensor and fuel injectors. I've also checked fuel pressure before & after the filter. All tests pass and do not indicate faulty parts/sensors.

The timing belt was installed per FSM. Although ignition set for 20 degrees BTDC, the timing seems to have drifted to closer to 30 degrees BTDC when using a timing light. I've also connected the timing light to other spark plug wires and they seem to be missing signals based an inconsistent/irregular light strobe at times. Some cylinders seem worse than others. Another odd thing is that cylinder bank 1-3-5 gets noticeably hotter than the bank for cylinders 2-4-6. At this point I've checked the things I can think that may be causing the problem, but still have been able to identify the source.

Just recently we made a trip to the junkyard and tried swapping the crank angle sensor and its accompanying disc, as well as make the upgrade to a PRW-2 power transistor, but the changes had little to no effect on the running condition. I've included a video of a recent start - the car starts quick and strong but after a few seconds it runs extremely rough, often stalling itself out at idle.

Any thoughts/suggestions are welcome.
 

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From what I can hear and see, the car starts quickly and smoothly. Around the 15 second point in the video the engine starts to stumble and heads down hill.
As the "start systems" are shutting off something is going wrong

There may be a timing problem, and you should figure that out and fix it, but I don't believe that is causing your car to stall out.

This is most likely a fuel or fire problem. If the cas is bad, that cases timing, fuel, and fire issues.
What is failing the fuel injectors or the spark plugs?
With no other information, I would want to watch a fuel pressure gauge during the start/idle/stall process.

After a start/stall, as shown in video, will the car start again if the key is turned off then on, pause for 5 seconds, then start? Is the second run different?
What is the behavior if you open the throttle?
 
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