O2 Sensor Help
 

My 1994 Z/28 has been getting horrible gas mileage (9-11 MPG) I was told I should be getting high teens city and mid 20s highway MPG. I was told that there might be an exhaust leak causing the O2 sensors to read lean thus the PCM dumping too much gas into the motor. The car DOES smell really rich while I drive.

OK, so everything from my headers all the way back are all fairly new (less than a year old) and were installed by the previous owner. All looks really good and professional, but I am not going to take anything for granted. What would be the best way to check for an exhaust leak? What are some tell-tale signs? I also know that after installing the headers that the sensors should be replace once all the "newness" is burned off. I am not sure if the previous owner did this.

Where do I even look for these sensors? I found pictures on Shbox. Are there only those two? Do I not have any downstream sensors?

I just dumped a TON :icon_bricks: of $$$$$ into having a shop COMPLETELY redo my cooling system (ALL new). I would have spent the time doing it myself, but I have been uber busy at work. I am sure the wife would appreciate if I didn't have the shop take care of this one too.

your car has qty 2 O2 sensors and if you have long tubes, they will reside in the collector of the headers, 1 each side.

WRT to exhaust leak, that would be on the exhaust ports of the cylinder head where the leak would need to be to affect those O2's.

If you used dead soft aluminum header gaskets then you probably don't have a leak. But, it would sound like a ticking as rpm's increase if you have an exhaust leak

Was the car tuned after installing headers?

And the sensors would only need to be replaced if your LTs were ceramic coated after about 2 weeks of driving.

Of course, this is assuming the guy who installed the headers did in fact put the oxy sensors back on. No oxy sensors = running rich. Looking to make sure they are there is step one.

Not sure about the tune. The LTs are indeed Ceramic Coated and I am not sure if the O2s were replaced or not. I think I might just start with replacing them and see how things are then.

Camaro 69 - I am going to get the car up and check it out today. I can't just crawl up under there. it is lowered and I cannot fit under there far enough to check it out efficiently. Hopefully I have time after work. If not. I already have a lot of things to do on my car this weekend. I already have Saturday scheduled as Z/28 day.

running without O2 sensors........................OMFG

OP.......stick your head under there and check. If there aren't O2's then you'll need extensions and can get them at LSxTune.com - Professional Tuning for your LSx Powered Car or Truck and the 12 inch size are long enough

you can't connect the O2's without an extension once long tubes are in

Sensors schmensors. Aren't they just an unnecessary emissions thing anyway? ;)
I'm sure there are some uninformed guys who think so (nobody here though)!

OK, stuck my head under there as much as I could (she is lowered). Yes, the O2 sensors are there.

I noticed on the driver's side just opposite the sensor on the pipe there is a minuscule cut on the pipe to aid in getting one pipe ID over the OD of the other. It is literally "___" that big would that really be enough to cause the sensor to read lean? Welding seems like WAY OVERKILL for something like this. How would I go about fixing this? Would two stage epoxy type metal weld be OK for this or am I fretting too much over this and the hole is too small to even worry about. I am going to get the car up and check her out completely this weekend and see if I can find anything else. Any cool-guy tricks for finding exhaust leaks besides visual inspection and feeling for it?

pictures please. should be exhuast clamps on the connections. best to use band clamps. like said a tune at a place like this LT1 PCM Tuning - OBDI/OBDII PCM Tuning/Programming Service would be agreat idea. i would change 02 sensors. dont use bosch 02s on a lt1.
heres a band clamp on y pipe.

Attachment 20871

Craby, does that band clamp leak on you at all? I've used them before, but they're more designed for butt-joining two same sized pipes.
I see yours is a slip joint, and there's a gap between the clamp and smaller pipe.