Engine rattle/misfire on cold start

EGR Cooler and Pipe should be cleaned. This is one of the items which can cause the rattle.
Another is to make sure the engine goes through the warm up cycle and shuts off before one turns the engine/car off.

 

For some it has been eliminated by letting the car cycle through the warm before shutting it off, say when you just are moving it out of the garage into the driveway or some other short movement.

 

It could be anything that fouls the plugs. Coolant, oil or gas. Headgasket, valve seals or bad injectors. Maybe a bad ignition coil. Your codes are misfires but not frequent enough to set a check engine light. Usually coils are not intermittent and if it was oil or gas fouling the problem would typically occur frequently.

The actual rattle is the engine running erratically enough that the electric motors can not synchronize with the engine. A spring loaded damper that looks and functions much like a manual transmission clutch slips and rattles severely.

If it has only exhibited a start up rattle twice in six months then its a minor problem so far but definitely a sign. You could change the plugs if they have not been replaced yet at 103k. You could get an injector cleaning. Both are highly advised regardless of the rattle.

However the head gasket is still a suspect. Many start out leaking at a very low rate and can go months between rattles depending on the position of the cylinder at shutdown, thermal stresses, overheating, carbon buildup working to seal leaks, etc. You don't always have a "blown out" segment of the gasket. Many recommend a proper leakdown test to diagnose but honestly it could pass and still progress to an aggressive leak.

If this engine had a better gasket track record then the concern would not be there. But the problem is too prevalent due to arguable reasons from piston rings to egr fouling to carbon buildup to high speed driving.

Change the plugs and clean the injectors and consider a leakdown test.

 

Make absolutely sure..... that the antifreeze is not low at all......... mark it and look closely after driving...

 

And look for any white smoke at startup....... I replaced my HG about 6 weeks ago.....

your miles seem kinda low for HG...... typical / everything fine...go out one morning cars starts and sounds terrible for what seems like a eternity but only a few seconds...
white smoke
down a bit on fluid
misfire code ( i think it was cylinder 1 but could have been 2.... )

I hope it's not the dreaded HG.....

 

My is doing the same, but I have already done egr,plugs,manifold ect. It's none of that anyway. It's not the head gasket either. PCM is what I am thinking, is there a flash update available?

 

Someone used Bar's Stop Leak, sold by GM as coolant supplement tabs, and may have just staved off the dreaded HG problem. As soon as I notice coolant loss and verify it's not leaking out the cap, (as it was for the inverter coolant on ours due to a damaged o-ring), I'm going to substitute/top off with K-SEAL. Early on with small enough leak you have the biggest hope that the "miracle in a bottle" will work. To me it's like the yearly flu shot. (I'm a fainter and have to warn shot givers that I might faint any time I get a shot). When used as directed may cause some pain/discomfort but just might stop you from deadly flu/head gasket.

moto g(7) power ?

 

Just forestalling the inevitable, and creating a mess?

 

I want to liken it more to us getting old. We start developing issues, then maybe start taking vitamins, calcium tabs, high blood pressure medicine, etc. Yes, we could go the route and have a bypass or a heart transplant. But at around $13 (just checked recently at local Walmart) and unpleasant looking coolant, it's definitely worth a shot!

moto g(7) power ?