Exhaust smells bad...could O2 sensor be to blame?

[Mark Howard]

I couldn't find any info in the archives about how the O2 sensor affects the smell or composition of the exhaust gas.

My '88 Carrera has 100K on it, burns just alittle oil, and has a cat bypass (test pipe actually, with the sensor in the pipe). I am not sure how long the sensor has been in the car, but if it is like everything else the PO did, it is probably original. I have read here on PP that you should change the sensor every 40K to 50K. Does bad smelling exhaust indicate a bad sensor?

[KFC911]

Search on some recent threads relating to the exhaust smell after installing a euro premuffler (or in your case a test pipe). Sounds (err....Smells) like it's the removal of the cat. I'm going to install my premuffler soon, then I'll have first hand experience...KC

[Superman]

It sounds like you may have a rich mixture, in spite of the O2 sensor. This would suggest replacement of the sensor. Brand of gas may be impacting the fragrance, too.

[tshih]

Oxygen sensor does not affect exhaust smell since it's job is to detect oxygen in the exhaust (oxygen is odorless!). Its signal in form of a voltage ranging from 0.1 to 0.95volts directs the DME to dial back on fuel injection to achieve perfect ratio of about 14:1 air: fuel for burning under all load conditions. The bad smell like rotten eggs coming from most exhausts is due to poor quality high sulfur fuel being sold in your gas station and a poisoned catalytic converter. Change the gas and maybe the smell will go away. Changing the O2 sensor will be helpful for maintaining good fuel economy and good running of the engine as well as keep pollution within specs.

Tom

[efhughes3]

Define bad smell. If bad means that it smells rich, then I think it is the lack of a cat. I recently put on a euro premuff and a new 02, and I get a rich smell. This was confirmed by a couple of others in a recent thread. So, the cats do actually work.

[john70t]

A lean burn can smell bad too, can't it, if the cat isn't eating up those HCs (which it normally should do).
I have bad plug wires (i.e. missfire) and the exhaust makes my eyes water.

[Mark Howard]

The bad smell is not like rotten eggs, but more like a rich mixture. It is the kind of exhaust smell that permeates your clothing and doesn't go away until you take a shower. i have had the car for about 2 years (test pipe since I got it) and it has just recently (3 or 4 months) started smelling bad. As for plug wires and idle, the wires are probably original and I have a slightly rough idle as well. I use top quality Chevron from a new station in all my cars. No problem with the others.

Any other thoughts? I probably just need to adjust the valves, change the O2 sensor and plug wires and get a good tune up.

[Nathan M]

I put a test pipe on my car (which was previously odourless) and immediately got exactly the same rich, lingering smell which you're describing. I put it down to the lack of cat. I used the same O2 sensor so I'm going to try changing it as a matter of course, just to see if it will improve things. I'm glad I'm not the only one who's suffering!!

Let me know if your tune up helps.

Nathan