Running Rich.. getting poor!

**Kent Canary** · Friday 7th October 2005, 07:04

Hi all,

My S70 T5 SE is, more than likely, running rich. I say this because the engine management light is constantly coming on, with the rear 02 sensor being the culprit. Once before it was the MAF sensor, but that was sorted and hasnt reoccurred. Im not sure if the front 02 sensor has ever triggered, but its the 02 all the same.

Now this could either be a faulty sensor, yes? Or, there is some kind of problem where its taking in too rich a mixture and causing the fault code.

What can be done to try and aleviate this? Changing the sensor seems false economy if the cause is still goingn to be an issue.

Or, as is often the case, something completely different will be pointed out and I'll go "oh yeah!!' or something like that.

Im getting about 26 to 28 mpg which is probably about right however it cost me £62 to get to Norfolk and back and that was keeping it around 70 and driving more smoothly etc. I cant keep spending that! Believe me I would be devastated if the car had to go but..

**Kent Canary** · Friday 7th October 2005, 18:21

No ideas anyone? Checked the hoses nothing obviously loose or perished. Pushed in some loose connector behind the airbox and in front of the main fuses, no idea what that was though.

**SaffronC70** · Friday 7th October 2005, 18:36

Kent, I changed both my lambda sensors and it's returning an extra 30 miles to a tank.

On the motorway (80 crusie) I even saw 500 miles to empty !

It's a DIY job, although you need axle stands and either a long spanner or a hammer (I used hammer, lol)

Chris

PS. performance was improved (86k old sensors)

**Kent Canary** · Friday 7th October 2005, 18:45

Thanks for the reply Saffron, so you would anticipate its the sensors themselves.. otherwise the car is running fine, have to get them changed ASAP methinks..

**volvotuning** · Friday 7th October 2005, 18:49

Have you read the fault codes? You say that it's "more than likely running rich" - have you had this tested? Loads of things can make a car run rich, if at all it is running rich.

Adam.

**Kent Canary** · Friday 7th October 2005, 19:16

Yes, Ive had the codes read, which come up as o2 sensor, and yesterday I was told it was the rear sensor, and the suggestion at the time was that together with my percieved reduction in economy that it was running rich, hence the O2 sensor would trigger. In fairness, my MPG is probably about right - so is it the sensor itself I wondered.

I see what youre saying - hence the post really to see if there were any suggestions. The fact that it keeps recurring would suggest to me that there is either somekind of flow / emission problem or the sensor itself. What the reason would be if it was running rich is as I say, unknown to me, so no harm in asking I thought!

**volvotuning** · Friday 7th October 2005, 19:29

If it's a lambda sensor then it will be fueling incorrectly on closed loop, ie at idle and part throttle. Do you know what the fueling is at idle?

Adam.