I wanted to know what happens when the injector hold down bolts are not torqued down to spec, what problems would arise and could it be a reason for somewhat hard starting?

 

I copied the information below from post 19 in this thorough discussion about injector torque: [LINK]

Mild knocking with tall ICP numbers and a little bucking with mild acceleration or maintaining speed up a slight grade - that's 80-100 inch/pounds.

50-80 inch/pounds brings a bizarre knock at idle, with maybe a hint of a "tink" sound - and this is the first time you can see symptoms on the scan gauge: The IPR is slightly elevated at idle, it may even wander. This IPR symptom is an indication ICP is leaking. Get on it right now, do not pass go, etc.... Ignore this one piece of advice and you get a ride to the next phase.

Under 50 inch/pounds? This is a cup-shredding cloud maker - let me share that one with you: