The trailblazer has throttle body fuel injection. Not individual injectors.
I have a 2003 Trailblazer, and upon investigation, I come to learn that just before the infamous fan clutch goes out, it will start to make a ticking sound at idle. I thought it was a pulley or the belt, but within a month the fan clutch finally went. Locking up and sounding like my engine was revving too high as I drove. Repair cost vary, but make sure they use the upgraded fan clutch to avoid replacing it again in another 40,000 miles.
Possibly just an adjustment on the rockers. Hydraulic system. Hopefully that's it.
lifters
The fuel injectors make the ticking noise you hear at startup, especially when the engine is cold (colder temperatures).
What causes ticking, check engine light, and the check gauges sensor to come on in a 1999 Dodge Durango 5.2L SUV?
the ticking noise is a small exhaust leak close to the exhaust headers or exhaust pipe near the engine.
if ticking noise is in engine, u most likely have a worn hydraulic lifter. check oil for correct volume and viscocity
from which part of your engine is the ticking noise coming from. if is the TOP it would most likely be lifter noise.try using a thicker oil.
Try to locate the ticking noise. Is it the engine? Is it ticking when you are driving? When you are sitting still? It could be as simple as a stone stuck in yoru tire, everytime it hits the road it ticks. it could be a lifter in the engine. Try to be more specific as to where and when the ticking happens.
I have the same ticking noise and it seems to be louder on hotter days. I was told by the service tech it's due to the synthetic oil being thinner. I have my doubts, but that's what they said. Still researching for the answer myself.
the lifters may need adjusting or replacing. your engine not getting enough oil causes the lifters to make noise. not sure what motor you have in it but if it's an engine where you can tighten the lifters then you can buy a tool for it if you know what your doing
your battery is dead
Front hubs my be wearing out.