What might be causing a loss of power during engine warm up on 90 Skylark 3.3
On a cold engine, starting out from stop feels ok until after trans shifts to 2nd gear then a slight loss of power occurs for a split second. Moments later it happens again. And sometimes a third time until speed is held steady in 3rd gear, then ok if not accelerating. But if I push pedal 1/2 way or more there is 100% loss of power until gas pedal is released. Sounds like engine has shut off but returns to idle and light acceleration again produces very slight momentary power loss as first described.
After engine warm up, problem disappears. A month ago I replaced the IAC, which corrected a high idle problem. Has run fine until last week when the power loss started. Since then have checked the computer coolant sensor 5 Volt reference and ground circuit - both ok, sensor ohm test which was ok also, but since I had the sensor out to test it I just replaced it anyway. TPS voltage within range at closed throttle and rises incrimently as throttle is opened. Cleaned MAF with CRC MAF cleaner and did circuit test, which was ok.
Fuel filter was replaced recently. Fuel pressure normal and dead heads at +60 . Fuel volume good. No engine codes ever set. Never an engine miss, and great spark with a spark tester.
Again engine never shuts down. Seems like all injectors are killed under heavier acceleration but fuel pressure is maintained during problem. I do hear air being drawn in. After engine warms up - runs OK.
Any help would be greatly appreciated.