i have gremblins

[320olskol]

My 1995 s 320 long was idling fine but when car was under load it wood start to miss i pulled obd generic codes from car random miss fires all six cylinders . changed all plugs and car run fine for about 4 weeks. car now idles ruff jumping between 600 rpms and 800 rpms , under initial load misses then is fine at speed 45 80mph have not pulled any codes yet friend has the scanner. the car has new harness .can it be bad gas

[Dr. Bob]

I have had problems with coil over resitor and spark plug wires going bad especially after changing spark plugs may require new set of spark plug wires and coil resitor. if this not remedy may have faulty coil over

[Arthur Dalton]

Change the three coil/plug connectors under each coil. Common fault item on 104 DIS ignition system.

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[Mike Freeman]

What are the odds all the connectors failed at the same time?
Have the HFM system tested. Look for Adaptation values and airflow volume. You're looking for something common to all the cylinders.O2 sensor ,airflow meter or large vacuum leak.
Mike

[Arthur Dalton]

It is very common for the connectors to fail. They are not just connectors on HFM DIS ignition, they are resistors and they crap under load because the spring connector is just a friction fit on each of the 3 plugs under the coils.
What compounds the miss is this is a Waste Spark system, meaning the plugs are in SERIES for each coil, firing 2 cylinders . so a misfire can affect 2 cylinder even if just one connector is bad.
Also, make sure you did not use Plats on this engine ..that would be the same results.