I have owned my 240 for almost 5 years, and as long as I've driven it people have said it runs rich. Most non-car people would just say something weird like "oh I love the smell of gasoline", so it has been fairly noticeable. The idles are a bit weird as well, often dropping and fluctuating, and sometimes I get various codes related to lamda/fuel mixture.

The current sensor is made by Denso (a local company), and was spliced in by Clayton Volvo of Knoxville in 2006. Over the years the wires have broken a couple times and I've spliced them back together to stop the "check engine" light from popping up, but this time I think the sensor has just been dead and not tripping the check engine light. When I remove the sensor connectors the engine runs the same, and seems to even run somewhat better. No check engine light or anything besides the normal condensation from the tailpipe and gas smell.

What sensors do you all recommend/have the best luck with? I see a large amount of sensors online but am not sure what would be best. As a student I try to save some money but understand the need for quality parts. Here are a couple I have been looking at:

https://www.ebay.com/itm/14330364163...m=143303641631

https://www.ebay.com/itm/15360926406...m=153609264062

https://www.ebay.com/itm/12195529623...m=121955296237

https://www.ebay.com/itm/38314203496...m=383142034965

Any links to guide on replacement would be great as well. It seems to be pretty simple but it's always nice to have instructions just in case.

 

Get the Bosch one. You have a Bosch fuel injection system so the original sensor was Bosch. I usually buy my parts from vendors that specialize in Volvo parts. This is where I would buy mine

https://www.fcpeuro.com/products/vol...60-bosch-13034

Also, if you are running rich, check for exhaust leaks upstream of the oxygen sensor. These leaks will let in fresh air in the exhaust stream which is sensed by the ECU as a lean condition and will enrich the mixture.

 

Thanks! I figured Bosch would be best but have heard various things about Denso, and know people who work for them.

I replaced the exhaust manifold gaskets and flange gasket (had to double up on these) maybe around 2ish years ago. I have wet my hand and tired to feel for leaks but haven't come up with anything noticeable. The gaskets were originally replaced because the car was running the way it is, but was way more loud than it should have been. Many people said it sounded like a honda civic so that needed to change.

 

To find small exhaust leaks I use a piece of hose as a stethoscope. Check around where the exhaust manifold bolts to the head, where the downpipe connects to the exhaust manifold and where the catalytic convertor connects to the downpipe. This is where leaks tend to be.

 

I actually have a stethoscope in my car most of the time so I can look around. The flange gasket did leak at one time but hopefully that was sorted. All of the gaskets are new but failure is always a possibility. Currently my main issue is a o2 sensor that refuses to budge after freezing, heating, soaking, etc. And of course it ended up getting chewed up and rounded even with proper tools.. When the new sensor comes I will have to take it somewhere to get the o2 sensor out.

 

Last resort is a pipe wrench. You can get a cheap one at Harbor Freight. Might cost less than taking it to a shop. I have replaced the O2 sensor on multiple cars and surprisingly have had no problems getting them out. Whoever installed the last one must not have used anti-seize

 

I plan to take it in Tuesday, but have another issue with the car I will have to post about. One thing after another with this thing.