I have a 2004 5.3 trailblazer and i just replace the coils ,fuel injector spark plug , spark plug wires and fuel pump and when im at a red light or just not putting the car in gear it shakes

SOURCE: Engine is missing and shaking bad when idleing or driving slow

it's probably one of the coils , I'd buy one and try replacing one of the two there ! , let me know how ya make out !

SOURCE: engine cranks ,but no spark.

ain t many more parts to electrical system left... i had same problem once n it was my ignition modulator.located under distributer.**** i can t remember,i think my car would not turn overfrom that.or only other thing could be a fuse.i 'd check every fuse too .hope this might help.

SOURCE: Shaking/Jumping engine and loss of power going on higher grounds

The engine needs a correct air: gas ratio of 14.6:1 to perform.
You need to check out your Fuel distributor. The engine light is on since there is not a correct mixture then it reports through the Oxygen Sensor.
Other indication is at red light the engine is going to die.
You are losing power since there is not enough combustion efficiency due to incorrect Air gas ratio.

Testimonial: "Thanks for a detailed feedback, so basically I have to replace my fuel distributor? My o2 sensor seems to be fine but im not an expert so replace?"

SOURCE: 93 mustang lx turns over

I suggest you check for spark by taking a spark plug wire off one of the spark plugs and using one of your old plugs and crank it over and see, it wouldn't be the first time a module died on a Ford. Plus if you have a fuel pressure tester hook it up and check for proper pressure if no gauge just shoot a couple of squirts of engine start or carb spray in the intake if it starts something wrong with your fuel system recheck wiring conections if you don't hear fuel pump, turn on key from 3 to 5 seconds fuel pump should run to prime fuel rail then stop, if not check fuel system.

SOURCE: 2004 chevy trailblazer shaking really bad in drive and reverse, check engine light is flashing ...changed spark plugs and coils but didn't help

could be a sensor...have it scanned...sounds like the problem....and good luck.