Newb here looking for some input on getting rid of a misfire so I can pass smog test. Just did a valve job on my new to me '89 3vze . Complete head rebuilds, all new exhaust valves, re-manufactured fuel injectors, timing belt, cap, rotor, plugs, etc. Ignition timing is at 10 degrees. Runs surprisingly well. Idle test is good but has a bad no load misfire starting at about 2,025 RPM. All good up to 2,000 and runs fine with a load on it at all RPM's. No ecu fault codes. High speed smog test requires 2,200 RPM minimum.
Noticed today that the mis-fire does not occur unless the motor is fully warmed up. Also found after I shut it off for 15-20 minutes it did not have the mis-fire. Seem to only be when it fully warmed up. Any ideas?

The only thing I'm questioning is if a vacuum hose is possibly connected wrong at the intake manifold for the cluster f of switching valves on the passenger side fender. Connected them all back how the were but could have been wrong from the get go. Can't find a solid vacuum diagram for the '89. The only '89 FSM I can get my hands on only covers the 22R.

Any suggestions?

 

Start by figuring out which cylinder is dropping off.

 

Could be the coil, does it happen when there is rain or high moisture? Does the coil get really hot? temperature sensor lying to the ecu? Have you run the VAFM & TB resistance checks? (may be shot due to high mileage)