How many O2 sensors does my 2004 SS Supercharged have.? Thanks.

Wayne

 

Two- one in the rear exhaust manifold near the downpipe mating flange and one right after your catalytic converter in the stock downpipe.

The front one tells your PCM how rich or lean the car is running based off the amount of carbon in the exhaust and is pretty important for regular driving (provided you have a stock PCM). The rear one is there to simply let the PCM know if the catalytic converter is working (if it records too much carbon in the exhaust, it faults under the assumption that the catalytic converter isn't working).

 

Thank you, that is what I thought. I'm going to change out the front one and see if I get better gas mileage. I'm only getting 23mpg on the highway. I have tuned the car up with new plugs, wires, air filter, fuel filter, and pcv valve. The 98 Grand Prix GT I used to have got better than that on the highway.

What kind of mileage are you getting on the highway? Thanks.

Wayne

 

Both of my 3800s are modified- so keep that in mind.

My Monte gets 27 MPG cruising at 75 MPH with A/C on. My Regal gets 29 with the same. I attribute the 2 MPG difference to the 3.29 gears and bigger injectors in the Monte.

23 MPG is definitely low. The O2 sensor is a great idea. You may want to clean your MAF sensor with MAF cleaner as well- I'd bet doing these two things will go a long way towards recovering your MPG.

 

Actually my MAF sensor is new because my mechanic accidently left a vacuum line off and it was causing the car to stall and the MAF sensor code to come up. So, I bought a new AC-Delco sensor and installed it and after I still had problems is when we discovered the vacuum line problem. The car has 90,700 miles on it so I'm guessing the O2 sensor is getting close to the end of its useful life. Every other vehicle I have that I changed the O2 sensor in, got better mileage after the replacement. Thanks again for the info.

Wayne

 

I just got back from a trip to Texas for vacation and it was an eight hour drive to where we were going and the car got 25.86 mpg on the way down there and that was not running the AC except for the last 45 minutes of the trip. This was with the new AC-Delco precat O2 sensor installed. I guess this car just doesn't get good mileage. Driving around the five days I was there, only got me a little over 21mpg. On the trip back running the AC most of the trip got me 25.7 mpg. This was figuring the mpg by hand and not using the overhead display which was over by about 2mpg.

The car did run flawlessly and I put about 1200 miles on the car this trip. I've only put a little over 4,000 miles on it since I bought it last Dec.

Wayne

 

That still seems low, I have the same car but slightly modified and get over 30 highway (calculated by hand not overhead display). Actually my overhead display was reading 34mpg at 70mph for a good part of a drive today. My last 2 3800 powered cars (94 and 99 bonneville) also got the same mileage as my monte and weighted a lot more

21 sounds about right for around town though. I usually get between 20-22 city

Are you running high test? Maybe try a different brand of gas. I use to drive 35K+ miles a year and noticed mpg variations between different brands of gas. Shell seemed to get the best over all

 

That is still low like already mentioned. How fast were you cruising and what octane were you running?

For the record, I've recorded a little over 17mpg city (beating the crap out of it) and a little over 25mpg highway with my Monte.

 

I almost forgot, speed does play a big factor. I drove to Georgia and back in my old bonneville (2400 miles round trip). If I stayed between 65 and 75 I would get 30-32 mpg but if I went 75-85 it dropped down to 25-28 mpg.

 

I got 27 MPG on my last trip to NC in my Monte- A/C cranking the whole time and the car was loaded with vacation stuff. 25 does seem a bit low, especially with the A/C off.