R6_C5_CLS55

Guys, for some reason it seems that using Sunoco 104 unleaded (5 gallons 104 mixed with 13 gallons 93 octane = 96.06 octane) kills my front O2 sensors (bank 1 sensor 1 and bank 2 senosr 1). Has anyone had a similar experience or know what the deal is? I mix fuel just for an added measure of safety with the blower, especially when it is hot outside. I know leaded gas will kill the O2's and the cats, but I am using unleaded. I have been mixing for the past 3,000 miles and both sensors (bank 1 sensor 1 and bank 2 sensor 1) have died.

I get these codes and I know they are going:

P1133 Heated Oxygen Sensor (HO2S) Insufficient Switching Bank 1 Sensor 1
P1153 Heated Oxygen Sensor (HO2S) Insufficient Switching Bank 2 Sensor 1

Looking at the O2 voltage with AutoTap (EFI Live) shows the amplitude of the voltage oscillation at idle is low.

Any ideas or recommendations (besides not mixing in 104 unleaded anymore)?

Thanks

lost

When I lived where Sunoco was available, I used it frequently to get max performance out of my SC Buick GS, never had a problem. My guess is that you are getting leaded fuel. As I recall the unleaded was 100 octane and 104 was leaded race gas.

Crushinator

I filled my tank with 1/2 Sunoco 94 and 1/2 Sunoco 104 one time. Never had a problem. It didn't help performance at all, but it worked fine. :confused:

kwik8racr

I run the Sunoco unleaded mixed with 93 everytime I go to the track, never had a problem!

gonbad

If it killed the O2 sensors then it is likely that they gave you the wrong fuel. If this is the case then you will have bigger problems as the catalyst in your converters is now coated with lead and will not work properly and will have to be replaced which is very expensive.

$$$frumnuttin'

In my area Sunoco sells unleaded laced with ethanol. I discovered this once when I saw gas prices way lower than any other station. They don't advertise it much, but there it was right on the pump. Got my butt out of there ASAP.

BlueDragon

Hum, I have had a similar experience with octane boost! but it did not kill the sensors it caused the low idle and a miss at idle and coated the plugs. I use 76 91 octane with ethanol (calif) and I refuse the other gas as it is MTBE. My plugs had a red coating and my fuel tables were screwed! This happened twice. The o2 sensors are ok, but it did throw misfire codes?? I know other guys doing the same thing with no problem?? I would add a full bottle of 104 boost to 3/4 tak of gas just prior to a race (I autocross a lot). The car would run fine the day I raced, but after that the rough idle would show up. I just stopped using it as it did not seem to be doing much anyway.
Jerry :skep: :skep:

catbert

Don't think any unleaded straight gas will kill the O2...something's fishy :lolg: