Some who are in the process of fixing up a classic car might choose to install a modern fuel-injection system in place of the old carburetor. Fuel injection is more-friendly for those without experience tuning an engine, but it also creates the need for an oxygen sensor.
And the placement and installation of that sensor are crucial to engine performance.
As Tome Kise from Holley points out in the video above, there’s certainly a right way and a wrong way to place the sensor.
The sensor should be located 6-8 inches after the collector, with 18-24 inches of exhaust pipe after it. As Kise explains, that’s the ideal location for the sensor to monitor the unburned oxygen in the exhaust while also preventing ambient oxygen creeping up the exhaust pipe and throwing off the readings.
Several installation methods can be used: For those who don’t have welding skills, a clamp-on stainless steel mounting bung is a good bet. The bung is threaded so the sensor can be screwed into place, the hole is made using a drill and two clamps hold the bung — as well as a high-temperature gasket — in place. It’s fairly straightforward and can be used as either a temporary or permanent solution.
Those who have some welding experience can either weld the clamp-on bung directly to the exhaust pipe or drill a hole and weld in a ring bung.
As simple as that sounds, Kise highlighted numerous ways an install could go awry. Installing the sensor too close to the exhaust merge doesn’t take an accurate sample. A bad or burn-through weld could allow too much oxygen into the exhaust system and cause false readings. The classic hose-clamp-and-pop-can exhaust patch that didn’t bother a carburetor will affect an oxygen sensor.
Poor-fitting flanges, installations done using coat hanger or JB Weld and other issues also don’t play well with oxygen sensors.
When it comes to wiring the oxygen sensor, be sure the wires are kept away from high-heat areas and won’t get caught or pinched anywhere.
It’s also important to read any warnings and labels that come with the sensor. Some can be ruined in under a minute if the system is not programmed before installation.
Other factors — such as excessive fuel, oil-control issues and additives or chemicals — also can foul the sensor. Solving those issues are key, as they can cause sensor after sensor to fail.
A typical sign that an oxygen sensor has gone bad is that it will suddenly read dead lean. That’s caused by the sensor getting clogged up and not being able to properly analyze exhaust fumes.