Watching my GL indicator (S4 NA) blink around, I realized that a lot of the time around town, my engine isn't going into closed loop mode. Even on the highway, it takes a while to start blinking rapidly.

It seems like my oxygen sensor (5000 miles or less on it) just isn't heating up enough to work well until a while after I get on the highway. I don't drive my '7 around town much because the fuel economy blows - turns out that in my normal driving, it never even warms up enough to be useful.

Has anyone tried using a heated O2 sensor, and if so, did it help fuel economy noticeably?

-=Russ=-

 

You must have disabled your 3K startup, lol. Put a meter on the O2 sensor's input at the ECU, and you'll get an idea of just how fast they warm up, and how much throttle at idle it takes to get her putting out good voltages. The 3K warmup system gets her pushing "ballpark" voltages before the system ever cuts out. If you're starting her cold without the fast idle, it takes about 10 seconds of high idle (maybe 2K & up) to get her going.

Also note that it takes a couple of seconds after the cruise "mode" is entered for the ECU to finally kick her into closed loop. Again, you can see all of this with a meter at the ECU, or I would imagine a good quality A/F meter would show you the same thing...

 

I didn't disable it... I just don't let it kick in. Not a fan of my engine revving to 3k when stone cold.

I'll take a look at it. Even when getting on the highway, it takes a few minutes for it to start cycling faster than 1-2hz (I understand it should be 5-10hz). Maybe all the premix is clogging it? I tend to err on the side of more premix in the gas.

-=Russ=-

 

Lol, I like using just a bit more premix than usually recommended, too. Gas mileage goes up a bit, believe it or not. Only drawback is the premix-in-the-oil gig...Never had a problem clogging the O2 sensor, though...

I've never seen anything "faster" than about 5 hz, even with a new sensor. Open loop cycling runs about 1/2 speed compared to closed loop, I've noticed...

 

premix-in-the-oil?

 

Lol, what most guys would call gas in the oil, due to the blowby, which is exasperated when using over-abundant premix. My personal theory is that side housing wear is primarily responsible for this, because everything else in my engine is new

I'd rather have longer engine life due to less friction and having to change the oil more frequently, though, than not use enough. But that's me...

 

I change my oil every 2000 miles or so, which has been leading to a LOT of oil changes lately.

The way I look at it, premix & more frequent oil changes are a LOT less expensive/annoying than having to rebuild the motor again.

My GL light starts cycling at 4-5hz on the highway. I guess that's about right, then. I'll try cranking it up a bit more on startup and see if that helps things heat up faster.

-=Russ=-