I4 Manual engine issues
Hi, new here. Ive been scouring the internet for some information. I have a 2008 Colorado, 2.9 I4 WT manual that I have 73000 miles on. Recently when I start it it will make a noise kind of like metal hitting metal. It only happens for literally one or two seconds when I start then goes away. And it's not everytime. Also it doesn't matter if it's cold or warm outside, or if I cold start it or it's been running for some time. It's not a grinding so it's not the starter sticking. It's like a weird knocking noise, but it's not the same sound as rods knocking. Also, the rpms start at around 1100 and will fluctuate up and down until it's around 750-800. I don't know if that's normal or not. Of course today it hasn't been doing it. Also if I rev it up to about 2500-3000 and let off, it'll sound kind of like it's backfiring in the exhaust. I'm honestly stumped on what it is. I know when I first got it I had to replace the vvt sensor because it was causing it to die when the rpms fluctuated too much (up until it decided it wanted to vary the rpms at idle at a swing of almost 800rpms) When I can I've been video recording every start up and when I can catch it I'll post a video, but does anyone have any ideas? Thanks!