1990 Nissan 300zx 2+2 NA


While cruising at 30 to 60 mph it is missing. While doing a slow or aggressive acceleration there is no missing. It only happens while cruising at moderate speed after the car warms up. Doe not do this when cold.

At 70 mph or above there is no missing.

I installed NEW- spark plugs,coil packs,and MAF. No joy.

All injectors tested and I replaced 2 that were bad.

I took it to a Nissan dealership service department. They worked on it for 1 1/2 days and did not fix it.
Colud it be a PTU?
Any help, suggestions, or theories would surely be appreciated.