Thursday, May 18, 2017

Hey all you Harley mechanics

The bike has been running rough, and stalling now and again when I come to a stop.  The diagnostics show a P0152 code, which Google says is a bad Oxygen sensor.  Makes sense, with rough idling and occasional stalling.

Has anyone out there ever changed the O2 sensors?  It looks like they're pretty easy to get to, and doing it myself would save the cost of the mechanic.  Thoughts?

8 comments:

Rev. Paul said...
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burt said...

I'll assume this is a new problem, not an old problem.

To answer your first question: The O2 sensors are installed in the exhaust manifolds. They are easy to remove: unplug, gently unscrew, screw in the new ones (remember to put antiseize compound on the threads), plug back in. Make sure that you install them correctly: swapping the front and rear O2 sensors *could* cause the engine to run poorly.

But I doubt that the problem is a bad O2 sensor. I'd look for other causes first: using less than 91 octane or using "bad gas", possibly a filthy air cleaner (when was the last time you cleaned it?), overfilled oil (if it's blowing oil into the air filter, it's overfilled), and anything else in the air path or fuel path.

You bought this used, right? Do you know if the previous owner installed a fuel management system (Arlen Ness, Vance and Hines, Dynojet, etc)? If so, it may be out of adjustment and you might need to load a new map or tweak its settings.

Rough idle and occasional stalling sound more like fuel or AFR problems than O2 sensor problems - but the ECM can only detect that there's something wrong with your fuel burn, so it points at the O2 sensor.

BTW: if your bike is post-2007, your O2 sensors are used by the ECM in closed-loop mode to make sure that the air/fuel mixture isn't too rich/lean at low RPMs. When the bike warms up or runs at higher RPMs, the EFI uses "fixed mapping" and mostly ignores the O2 sensor readings.

selsey.steve said...

The O2 sensors, properly called the lambda sensors, should be replaced every fifteen to twenty thousand miles or so. They operate in the most hostile of engine environments, just downstream of the fuel explosions, with extremely hot, corrosive gases passing by at very high speeds. Replacing them is good.
I'm not familiar with the HD set-up with lanbda sensors but having one up-stream and another down-stream sounds a bit excessive. Do both sensors measure the same thing? If so, why?

Borepatch said...

Steve, I think I just have one per pipe. V-Twin, two cylinders, two pipes, two O2 sensors.

Will said...

It's common for the O2 sensor thread to already have anti-seize applied at the factory. Usually with a plastic cap to keep it unmolested. Make sure it's there in some fashion before installing.

There is a special, very deep (22mm) socket, with side slot for the cable to clear, that is used for the auto applications. On a bike, you may be able to use an open end wrench. The harness connector may not clear a box end wrench. Some applications require you to move the old connector to the new sensor. The sensors tend to be generic, with just the number of wires, and harness length varying. You tend to pay big bucks to get an OEM connector equipped sensor.

Goober said...

It is as easy as changing a spark plug. With the caveat that it is not uncommon for the threads to be seized due to high manifold temps. Bring penetrating oil and go to town. You got this.

jon spencer said...

When you do swap it out, use a nickel anti seize. It has a higher temp. rating than copper based anti seize.

Tom said...

I can't imagine HDs run much different than other bikes, unplug both and forget about them. The ECU will run in default mode and richen up the A/F mix slightly. This is a positive net gain.