So, I started to notice mild pinging about 5K miles ago. Usually at mid and highway speeds when accelerating. I usually run Sunoco 89, but jumped up to 91 with hopes of shutting the pinging down. The cel came on about 800 miles ago. At that time, I was mired in 15 hour workdays, 7 days a week, so I just couldn't attend to the O2 sensors. Plus, it's been ****** freezing in NY up until now. I can't get the T into the garage with the high cap installed. In addition, I haven't had the chance to do much more than local driving, so the pinging wasn't obvious. The jobsite was less than 5 minutes from home! So, the other day, I got both O2 sensors (Denso) installed. I had to put some mileage on it before inspection that day so I took it for a nice ride. Whether local or on the highway, I couldn't make it ping if I tried!

If it's so that O2 sensors could have such an effect, even without a cel, is there a way to check them? Will a tired, yet not yet faulty O2 sensor somehow register on a scan?

On a side note: I bought a brand new '03 Tacoma X-tra cab TRD Offroad 3.4 V6. Silver. Beautiful truck. Loaded and expensive. At about 1.5K miles it started pinging. I only use quality gas. I tried changing brands, upping octane, nothing worked. It drove me nuts. Toyota was no help. I went to war with them. They tried to blame it on ticking injectors at first. When I finally got the regional tech in the truck, he had to agree with me, but would do nothing. Called it normal. Told me that I have a platinum warranty and don't worry about it. *****! It's one of the things that made me hate that truck and get rid of it. A bad memory that I don't even include in my sig line! Anyway, I suppose it's possible that I had a half ****** O2 sensor in that truck. Just maybe? Possibly?

Gone!

Rich

ALL O2 sensors 'drift' over time. They degrade slowly but predictably; high temps and contaminates [Silicon, Phosphorous, etc.] in the exhaust are the main culprits.

Winter gas is oxygenated to further reduce CO emissions. It has lower BTU content per gallon - that is why your mpg drops, you need more gallons for the same energy to drive X miles.

Hot rodded 2 cycle snowmobile and boat engines used to burn pistons from overlean A/F before folks learned to deal with the extra O2 in reformulated gasolines.

So - it is very possible that an 'old' O2 sensor with a lean drift bias coupled with oxygenated fuel could make your engine run overlean - extra heat from lean mixture may contribute to the pinging.

Check your spark plugs for color and condition - they would be the best indicator of sustained lean/hot operation.

RichO- I understand your frustration, but lets try to keep this site "family friendly." <img src="/forums/images/graemlins/kewl.gif" alt="" />

I edited your post...

Something you may want to consider... Octane ratings are simply a measurement of the heat/pressure index that the gasoline can withstand before detonation. The higher the rating, the greater heat/pressure it can take. That said, the timing on your computer-controlled, fuel injected motor was set at the factory for a particular grade of gas (in our case, 87 octane). Take a peek at your owner's manual to confirm...

In essence, what you are doing by running a higher than recommended octane is simply wasting money, both in the price per gallon as well as miles per gallon (doesn't burn at exactly the same rate - your motor has to really retard the timing to compensate). Stick with a reputable station's 87. Resetting your ECU would be the quickest/easiest way to get everything back to normal. Give it a few days, then see where you're at.

The concept 'price = quality' doesn't really carry over to fuel - a bit of a misnomer that has been fed to the public... Kind of like 3k mile oil changes! <img src="/forums/images/graemlins/lol.gif" alt="" /> Your typical fuel has 0 personality until it arrives at the blender (last hop before retail distribution), at which time it receives the specialty additives to 'brand' it (Chevron to Techron, Shell to V-Power, etc...). More often than not, oil companies will 'market-trade' their stock of refined fuel, so it may have come from any number of refineries.

Good point on octane - premium high octane fuel also has lower BTU content per gallon - unless you have the high compression ratio [or turbo] which increases the engine's thermodynamic efficiency you are immediately losing fuel economy by using 'low BTU' gasoiline.