I own a 2002 Chevy Trailblazer with 4200 vortec engine. Runs rough at idle and slow with acceleration. Had Check Engine Soon Light with P0301 code.Had O2 sensor changed, throttle plate cleaned and spark plug wires changed. Still runs rough???

11.2 quarts from dry, including torque converter. When just changing the filter, between 5-7 quarts. Dexron 6 is the best, and newest technology from GM.

You have an inline six engine and it is equipped with engine-mounted electronic Powertrain Control Module that records hundreds of measurements per second and makes immediate adjustments of air, fuel, spark control, and valve timing to provide optimal engine operation. Your Vortec 4200 uses an electronic throttle control (ETC). The ETC sends a series of signals from an accelerator-pedal module using a sensor that relays acceleration-intent data to the powertrain control module (PCM).
To increase idle you will have to reprogram the PCM using an OBD 2 software. Have it service at your dealer.

Usually means the engine bearings are worn out, or the oil pump is weak.
As the oil gets hot, it gets thinner, which reduces pressure. When the engine is at idle speed the pump is not pumping as fast as it is at highway speed.

Read the fault codes and replace faulty units.

still sounds like another sensor is bad. take it to shop and have it tested would be my suggestion. good luck.....

you have a vaccum leak, or a vaccum line came unhooked

Rough idle can be caused by dirt in throttle body or EGR system, but there are many other possibilities. The service engine light indicates the computer has detected a fault. If you can get a free scan at your local parts chain and post the trouble codes to us we can give you more specific repair recommendations.

Have you checked for any codes? Is the check engine light on? If there is any codes it will give you an idea of what to look for.

it could be an o2 sensor. it could also just need a tune up

This one is easy. The clutch fan is not disengaging. Mine does the same thing after it has idled a while but then will release (wind noise stops) after getting up to speed.