have you checked to see if there is any broken bolt on the manifold, or worped manifold, burnt manifold gasket
The starter is on the left side (inside) of the engine underneath the exhaust manifold.
The oxygen sensor is in the rear exhaust manifold. You should be able to see it by looking behind the engine from inside the engine bay.
Oxygen sensors are located in exhaust manifolds or in exhaust pipes before and after the converters in most cars depending on the year of the vehicle take the manifold loose from the engine and it is inside it
Look inside the engine compartment and see if there's a turbocharger between the exhaust manifold and the tail pipe.
There are a number of oxygen sensors on the 1997 Cadillac STS. These are found on the firewall, inside the exhaust manifold, and behind the catalytic converter depending on the engine model.
That is the charge air pipe.It has four nuts where is connects onto the exhaust manifold and also ties into the exhaust collector mounted directly below going to the exhaust system.The charge air pipe goes to the housing on the front of the air cleaner housing which has three air filters inside the housing.
Its not a spin on type filter, its inside a housing on the left side of the exhaust manifold
The camshaft position sensor on a 4.3L engine is inside the distributor near the rear of the engine. Has the intake manifold gasket been replaced? Sometimes it is overlooked to plug the sensor back in after this repair has been done.
Noisy exhaust, exhaust smells entering passenger compartment. holes rusted seam, or if the engine has been backfired it will appear swelled up near the middle also if it makes a rattle sound when struck it may have loose or broken baffles inside
there are two oxygen sensors. One is located in the exhaust manifold inside the engine compartment. If you have a 4 cyl model it will be where the 4 pipes merge in to 1. The second sensor is located after the catalytic converter.
Gain access to the manifold area, Unbolt the 6 bolts holding it on. Seperate the manifold from the engine and scrape off the old gasket, sand it down with emery cloth, Make sure to keep debris from going inside the chamber. Insert the new gasket and get the manifold close then wiggle it around till you can get a few bolts in then thread the rest in. torque them down to spec and your done.
Blue smoke from any car usually means that engine oil is being burnt, either inside the cylinder or on a hot surface such as the exhaust manifold, you need to ckeck for an oil leak, blown gasket etc.