Intermittent operation of an O2 sensor could be because the electrical connector is not very tight, comes loose occasionally.

 

I double checked the connection and it doesn't seem to change when I wiggle the wires. But if something was wrong with the connection wouldn't it read 0 volts instead of being low and fluctuating slightly?

 

I did the soap/shop vac test again after starting the car, and it shows an exhaust leak again between the manifolds and the exhaust pipes. I tightened the bolts and the gaskets there are new. How can I fix the leak?

 

Do you have locknuts on? I have good results with the Remflex gaskets from Amazon

Exhaust Gasket-LAND ROVER Exhaust Manifold-to-Front

 

Not necessarily, no. Depends on the particular issue. Disconnecting and reconnecting a few times can often solve an intermittent connection problem.

 

That is a good point. Maybe swap O2 sensors to see if the problem swaps, meaning bad sensor.

 

What do you mean by having lockouts on? Does the gasket you recommended work when the standard one does not? The gaskets on it now are new generic ones.

 

I think I found an intake leak as well. I heard a hissing noise on the valve cover side of the hose that connects from the valve cover to the plenum. Moving the hose seems to change the hissing. I tried tightening the clamps, but that didn't work, so I'll probably order a new one.

Is this hose even the one that is supposed to be for this? It doesn't fit on the valve cover thing all the way, and looks different from the one online.

 

The factory nuts are crimp nuts and should not loosen after tightening. Those gaskets are 3-4 times thicker than factory.

 

Which hose specifically is hissing? The larger rubber hose going from the intake to the valve cover, or the thinner smoother plastic piece?