Yes, missing a bolt on the intake manifold will absolutely cause an intake leak which will cause poor, rough idle conditions. Also the coolant loss could be leaking from the coolant crossover tube which is an aluminum tube that goes from cylinder head to cylinder head on the front of the intake manifold. If coolant is leaking from here there is a distinct possibility that it is leaking into multiple spark plug tubes. I have a 4.6L engine in my mustang, which is basically the same engine, just different cylinder heads, and these engines are famous for this. If there is any coolant in the spark plug tubes it will cause a misfire and rough unstable idle. The EGR connections at the throttle body must be tight with a gasket in place as this is also a potential intake leak. So let's pick a corner and start. Replace the intake manifold bolt. The best way to do this is to remove a good intake manifold bolt and go to the hardware store. Match it up to a similar bolt in the fastener section and install both bolts. I have included the torque specs in the diagrams down below for you.
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Friday, April 19th, 2019 AT 6:56 PM