V50 General : 1.8L petrol failed emissions badly

[thecuist]

Hi all
Looking for some technical input as to possible reason for my V50 failing its emissions terribly.
Information to hopefully help:
Volvo V50 2005 reg 1.8L petrol (NOT bi-fuel)

Low Idle:
CO = 3.91%
HC = 1,114ppm

High Idle:
Lambda = 0.86

The testing station said they had to abort the rest of the test because their equipment was getting blocked up because the readings were so high.

The car has done 150K miles but only 2 owners from new and the last owner appears to have kept up with servicing very well and car appears to have been well looked after.

Fuel economy appears to be about right, she is running at around 7L/100km which equates to 40mpg which seems about right considering the mileage and the fact that she is running very rich. There are no warning lights lit on the dash and I know the MIL light is functioning because it lit up briefly after a very flat battery but then went out after a good run.

So far I have checked as best I can all vacuum hoses and cant see anything out of place. Engine seems to be running smoothly with no misfire and no lack of power. I then checked the front oxygen sensor using a digital multimeter with engine fully warmed up. There seems to be correct resistance on the two white wires for the heating element, but the voltage reading on the sensor wires is cycling from 0 - 0.350 mv approx once a second which If I understand correctly indicates running lean. This would then send a signal to ecu to pump in more fuel which would explain the running rich I think. But, surely if the engine is running rich as shown by the emissions test, then that lambda sensor should be reading rich i.e closer to 1V. Therefore would i be right in thinking that the front lambda sensor is reading faulty i.e lean when it should be reading rich and therefore is faulty??
Sorry for the length of this post but im getting nothing but iffs buts and maybe, from local garages who are saying things like hmmm could be knackered engine, could be knackered CAT, could be knackered Lambda, and they all glaze over when I start talking about Lambda voltages. lol.

[mattievrs]

Could be anything really mate, but I'd start with changing the lambda sensors first then see what it reads then. Could be burning oil, could be a failed cat convertor, the list is endless really. As I said though, change the lambda then rag it hard to get the cat really hot and put it through an emissions test and see.

[pgm]

I would get it checked with Vida/dice and someone who knows what they are doing. Might save you a lot of time and trouble in the long run.

Paul

[kebab10]

Why not start with the basics? How old are the plugs? Are they genuine Volvo ones correctly gapped? Fuel consumption maybe okay even with less than ideal plugs, BUT Volvo plugs are best in these cars. Dont forget the air filter either. Basics, then faff about with these lambda voltages.

Hope my twopenneth helps.

[Daim]

Get on the road and give it some welly! High revs low speed etc. - looks like a catalytic convert or not working properly due to age... Then head to get it checked by a Workshop again. How was the emissionstest done? Via OBD or sond up exhaust?

[T5R92011]

I'd go for new lamba sensors and Cat.... though i would suggest avoiding any cheap ebay cat as they tend to do the bare minimum in terms of pollution reduction.

[thecuist]

Firstly thanks to everyone for their comments, heres an update on the situation. Took it to a diagnostics specialist and so far we have changed the plugs for new iridium tipped longlife £15 a pop. OUCH.
He did a smoke test for air leaks and found none.
We verified that the o2 sensors are reading correctly (very rich)
Changed oil and filter because he suggested that with that much unburnt fuel the oil could be contaminated and be throwing the readings out, HC readings have dropped from near 1200ppm to about 600ppm which is still 400ppm above minimum requirement for emissions.
He checked injectors for leaks and says they are all ok.
Only fault code coming up is o2 sensor reading out of range rich, and the sine wave on oscilloscope shows the same.
We are pretty sure its not a CAT issue because the upstream o2 sensor is showing rich and is trying to lean back the fuel to compensate but cant lean it enough so its switching to open loop operation, which as I understand it means that it goes to a default base ECU map and stops using the o2 sensor signals to control mixture.
So now I'm thinking possible worn injectors/high fuel pressure, or possible MAP sensor issues.
I know the injectors aren't leaking but is it possible to have worn injectors which dont leak? and if fuel pressure was too high could that cause too much fuel to be delivered.
Any thoughts? Is there a way to test for worn injectors without buying replacements and testing emissions afterwards, and what should the fuel pressure be at the rail?

[KBB]

Note you state the O2 sensor is stuck rich, create a lean condition by removing the brake servo hose and see if the sensor reacts and if it dose the STFT will start going positive proving the sensor is good and the fault lies else ware.

Is the sensor proves good then locate the hose running from the EVAP canister to the manifold and clamp it off, if the trims start going positive then the EVAP control valve is likely stuck open so permanently drawing fumes from the tank.

[thecuist]

Thanks KBB
I think we have managed to successfully prove that the upstream o2 sensor is good. I initially thought it was stuck lean, but when the tech plugged into the OBD port we were able to see the trace from the sensor making a proper sine wave. And then if I recall correctly when we raised the RPM it settled near the top approaching 1V. I will definitely suggest to him that we do that evap cannister test you outline. I hadn't come across that as a possible reason for the running rich in all my internet searches. But it makes perfect sense. I wish I had all the diagnostic kit myself because its always difficult trying to suggest to a mechanic how to do his job, but he seems like a pretty reasonable chap so should be ok.

[jeffmasson]

Originally Posted by thecuist

Firstly thanks to everyone for their comments, heres an update on the situation. Took it to a diagnostics specialist and so far we have changed the plugs for new iridium tipped longlife £15 a pop. OUCH.
He did a smoke test for air leaks and found none.
We verified that the o2 sensors are reading correctly (very rich)
Changed oil and filter because he suggested that with that much unburnt fuel the oil could be contaminated and be throwing the readings out, HC readings have dropped from near 1200ppm to about 600ppm which is still 400ppm above minimum requirement for emissions.
He checked injectors for leaks and says they are all ok.
Only fault code coming up is o2 sensor reading out of range rich, and the sine wave on oscilloscope shows the same.
We are pretty sure its not a CAT issue because the upstream o2 sensor is showing rich and is trying to lean back the fuel to compensate but cant lean it enough so its switching to open loop operation, which as I understand it means that it goes to a default base ECU map and stops using the o2 sensor signals to control mixture.
So now I'm thinking possible worn injectors/high fuel pressure, or possible MAP sensor issues.
I know the injectors aren't leaking but is it possible to have worn injectors which dont leak? and if fuel pressure was too high could that cause too much fuel to be delivered.
Any thoughts? Is there a way to test for worn injectors without buying replacements and testing emissions afterwards, and what should the fuel pressure be at the rail?

All ready said but I am going to repeat as its well worth a try and get it plug into Vida as it my have Volvo only faults that's will not show up with a obd2 or put up a mil. £75 on eBay if you know your computers or find a member near by. Or take it to a Volvo specialist as they will have the kit.

Well worth the £75 as the software has a full parts list and workshop manual as well. Just a pita to get working so not for a novice computer user.

Good luck