I have a 2004 Chevy trailblazer vortec 4.2 inline 6 2wd with about 170k miles (gauge cluster doesnt work like typical GM from that era) but the other day i started it for the first time in a week so it was definitely cold. What was weird though was the engine was idling very low for it being cold, id say it was even lower than a warm idle. Cant say exactly what the RPMS was because the tachometer ofc doesnt work, but it was definitely much lower than it should be id say around 400-600rpm Plus the car was vibrating as wel during idle. I changed the ignition coils and spark plugs about 15 thousand miles ago (just for added info). Any ideas as to what my issue might be?
-Thanks
Check operation of your IAC valve. Ideally you would use a bidirectional scan took (Tech2 or equivalent) for testing.
It looks like in that vehicle the IAC is integral to the throttle body and they are serviced as a unit. (In other words if the IAC valve is bad you have to replace the entire throttle body.) Maybe cleaning the throttle body would help in case some accumulated gunk in there is causing problems.
check the fuel pressure
