Manifold Gasket & Oxygen Sensor????

What's the easiest way to check for a manifold gasket leak and also if an oxygen sensor was bad, shouldn't you get a code for this? I have a 1992 s-10 Blazer 4.3 vortec - v-6.

an old trick is to use a can of starting fluid.

Start the motor and spray sparingly around the edges of the intake manifold, if you find a spot where the RMP increases when you spray, you've found a leak!

The O2 sensor sould set a code if it's bad.

the starting fluid works but brake cleans works better on finding a leaking intake

but if its a bad o2 i wont always set a code off in the computer
the o2 can become lazy, this will cause no code but what it does is switch at a extrmely low speed but switch enough no to cause trouble u will notice bad gas milage or good depending where it get stuck the most

No doubt brake cleaner works, as would many higly combustable products, but most of them have no lubricant in it, starting fluid (most brands anyhow) does.

use carb and choke cleaner