hey guys, im driving the 08 chevy colorado with the 2.9l 4 banger engine automatic trans with 50k on the odometer, and i believe that it has a misfiring issue. sometimes upon starting the truck it’ll idle for a little while then the rpms dip down low for a half or full second, and the whole truck will shake before returning to normal idle speed. also i can feel a slight imperfection in the idle which you can’t see on the rpms hand. while driving, when im slowly accelerating there’s a moment where it feels like a hard shift/extra shift accompanied by a quiet pop occasionally. no check engine light. most of the time when counting the shifts i get 5 gears, which is unusual since it’s only a 4-speed automatic (as far as i know lol). when accelerating harder that “extra/hard shift” goes away. already cleaned maf sensor, checked for vacuum leaks and threw royal purple in the tank but made no difference, so now im planning on cleaning the throttle body and changing the plugs, since i have to remove the resonator box which is a step to do both. but, with the oem iridium plugs being rated for 100k miles, and this 14 year old truck only having 50k miles, would y’all say it’s a good idea to go ahead with changing the plugs? please excuse this mess of a read
Don't forget to clean the throttle body and check that the linkage is operating smoothly.
Yes, it's a good idea to change the plugs - if nothing else, how the plugs look could give you an idea about how the engine is running and if there is one cylinder not doing well. Take a pic of the old ones and post it here for more opinions.
As far as the phantom 5th gear - when it's up to speed in 4th, the torque converter "locks up" to direct drive to improve gas mileage. That's why your RPMs drop and the sound changes.
i believe that it has a misfiring issue
that would throw a misfire code. Run diagnostics and check for pending codes.
slight imperfection in the idle
my idle is never perfectly even. There's all sorts of things going on. Electrical loads are switching on and off. AC compressor dis/engaging, computer switching fuel metering programs... etc. And I have a V8. A 4-cyl will be even rougher.
counting the shifts i get 5 gears,
you're probably feeling the torque converter clutch disengage.
You're driving a modern GM. It's never going to be perfect. 😆 Turn up the radio and ignore the little sounds.
