04 Chevy trailblazer problem

A faulty Throttle Position Sensor will cause engine to rev up high RPM before it changes gears from 1st to 2nd. These codes are popping up AFTER you replaced the plugs? A little oil isn't too bad, a lot would require you to replace the valve cover gasket.

Transmission solenoids get clogged. Thera are several f these.. Consider a major overhaul. If so, get these parts new and nto from the usual kit: transmission wire harness including factory mounted solenoids (2solenoids); high performance Bendix 3rd and 4th gears; all solenoid; and a heavy duty transmissiin BELL. Always replace transmission oil pump. This are expense you wont regret, aprox. +15% more on parts, labor should not change. This you won't regret as the investment is on wear and tear parts that tend to fail. This transmission, although a 4 gear, was standard on 80' Corvettes and is full of torque. The transmission bell and 3-4 gears are its weakness. Look at this as an invedtment. Ichanged to synthetic transmission oil an change it every 50-55k miles with filter. I tow a boat and it's been over 70k with a great performance, better than original.