If I had some cash to toss away, I'd just go ahead and buy a new O2 sensor for my 95 wagon. Is there a way to test if these things are operating correctly? I have no check engine light that has ever come on in this car. But, my gas mileage is horrible and the engine smells a bit like it's running rich. Could the O2 sensor be causing some problems for the engine's computer? Any other suggestions?

it you get that rotten egg smell

it's probably your cat, not your 02 sensor

 

either way, if something is amiss you will get a CEL soon enough

 

Jamie

JT95--how many miles on the car? Any idea if the O2 was ever changed? I've heard they can get weak after time without throwing a code. Changed mine at about 105k as prevention.

JT95--how many miles on the car? Any idea if the O2 was ever changed? I've heard they can get weak after time without throwing a code. Changed mine at about 105k as prevention.

 

 

The car just rolled 170,000. I don't know if it was ever changed, I did ask the previous owner some maintenance questions, but that wasn't one of them. I wish it would throw a check engine light so that would give me a code to investigate. I'm getting like 18-22 mpg and the engine has a fuelish smell to it--like it's running too rich. My wife says she can smell it on me after I've been on the road.

 

It's not a rotten egg exhaust smell. It's definitely something in the engine bay--not horribly strong, but enough to notice. My wife said she noticed a little less pep when she drove it from what it used to have.

 

Would a shop be able to do reliable diagnostics w/o me ever had a check engine light flash?

A fuel smell int eh engine bay may not be an o2 sensor. I'm thinking vapor recovery or something(though that would not in itself decrease fuel mileage I guess.). Might also be worth pulling the plugs to see if any of them are black or look different from the others. What other symptoms are there? Better or worse after warmup, starting, performance up hills, etc. I think bad engine temp sensor, MAF and bad front O2 can cause rich conditions.

 

Perhaps you have a coupla problems at the same time?

 

Others here may have some ideas.

 

Carl

If you have a Quality multimeter, you can back probe the O2 sensor and record the V as you drive. If you watch it you should see regular crossovers and voltage. Due a search for V values for rich and lean. I don't have them off the top of my head.

If you have a Quality multimeter, you can back probe the O2 sensor and record the V as you drive. If you watch it you should see regular crossovers and voltage. Due a search for V values for rich and lean. I don't have them off the top of my head.

 

I think the voltage values should rapidly oscillate between .2 volt and .9 volt