V70 T5 - not mine - overfuelling.

[Tetleysmooth]

A lad on another forum has asked me to post over here for hopefully some advice.
In his own words:

'Basically it runs very rich all the time. I start it up and it runs smooth, but the exhaust stinks of fuel, and it will start to stumble within a couple of minutes. Then it won't start for a couple of days because I assume the plugs are wet, so I'm assuming something is telling the car to add more fuel. Lambda sensor, Cat, vacuum issues and temp sensor are all possibilties I guess, but working out which one is difficult. I've changed the MAF and fuel pump relay recently'.

I suggested the temp sensor, but does anyone have any other ideas about this?
I'm pretty sure this is a phase 1 V70 T5.

[volvo again]

Maybe worth checking for split vacuum pipes as well...
Without proper diagnosis could be hard to find the cause and just replacing parts will work out expensive

[byootox]

Coolant sensor would be the first thing I'd check.

[jack taylor]

I had the same symptoms with my 1998 V70 and that was a faulty temp sensor

[SwissXC90]

I had similar problems on an old VW golf, and it was a broken wire to the engine temp sensor
The engine ECU thought it was maximum negative temperature and over-fuelled like crazy.

Was easy to find and fix.

[Tetleysmooth]

I've passed these replies on, so thanks people.

[PNuT]

If its that rich probably the front oxygen sensor

[KBB]

The are a number of possible causes for a very rich over fuel condition. If it that bad from start up then here is the approach I would take:

Live data at key on ECT temperature reading, alternative test is with sensor connected KEOE back probe ECT and look at voltage reading.

Live data at key on MAF reading.

Stuck open injector, fuel pressure gauge test rail pressure at key on to prime the rail, switch off and look at pressure decay rate, if its fast then likely injector stuck open.

Fuel pressure regulator, remove vacuum pipe if fuel spills out the diaphragm has split, spilling fuel straight into inlet manifold.

Fuel tank EVAP solenoid stuck open drawing fuel direct into manifold, disconnect and temporary block it off see if it starts.

All of the above mentioned faults will have created a lot of fuel contamination with the oil, so after repair he will need to change oil and filter, heavy over fuel conditions will lead to "bore wash" where excess fuel now in the cylinders removes the oil around the rings lowering compression and creating no start conditions.

Hope this helps

[sdg1970]

My R did similar last year and threw multiple 0172 & 0131 codes. It turned out it was a faulty temp sensor, causing the front o2 sensor to have a hissy fit. At one point it was down to 16mpg or less....

[Tetleysmooth]

Thanks for the further replies chaps, I've passed them on.