Hi guys,
My '97 850 just failed an emission test in Ontario.
Recently I have replaced the exhaust manifold due to a leak in the soft link. I also had P0133 (oxygen sensor B1S1 slow response) and P0140 (Sensor b1S2 no activity) ODB2 codes.
I went to a testing facility and failed with the following readings:

ASM2525 Test
HC: 58/54 PASS
CO%: 0.32/0.61 FAIL
NO: 435/202 PASS

Curb Idle Test
HC: 200/27 PASS
CO%: 1.00/0.06 PASS

After that I replaced both oxygen sensors, fire trap, new spark plugs, air filter, ran injector cleaner, and checked the vacuum hoses for leaks. Also, I cleared the codes but after driving about 50 km P0133 came up again. I cleared it again, disconnected the battery for 30 minutes, checked the ECU connections, cable connections, etc but this did not help. My CEL is on again with DTC P0133. Today I decided to try the emission test again and failed with the following:

ASM2525 Test
HC: 58/43 PASS
CO%: 0.32/0.46 FAIL
NO: 435/120 PASS

Curb Idle Test
HC: 200/20 PASS
CO%: 1.00/0.24 PASS

As you can see, the readings are slightly better but still not enough. I am not sure what else to do. Do I need to replace the cat or the problem is something else? I really hope to avoid going to the dealer at this moment.

More info about the car: volvo 850, 1997, 2.4 non turbo, 195000 KM, almost always driven with high grade gas.
Thanks alot

 

Did you replace clean the vent box system?

 

Check to see if you've missed something for tune-up at:

https://volvoforums.com/m_48928/tm.htm

CO level increases with less pressure & heat in the combustion chamber, but if you increase those two elements, NOx level increases accordingly so they have to be precisely balanced, meaning the emissions system has to work very precisely.

Did you replace the O2 sensors with direct-fit OEM Bosch sensors? If the combustion temp is low, the A/F mixture could be rich, thermostat in less than perfect condition, etc... Someone else has had the same problem recently, and you can find the thread within the first 5 pages or so I believe.

When was the last time the distributor cap & rotor and ignition wires were replaced? See other members would have different things to look for. 850s seem to have a bit too sensitive emissions control system.


JPN

 

Thanks for the answers.

I did not replace/clean the vent box system. Also, I have no idea when the dist cap, rotor and wires were replaced. I have got this car about 20 months ago (60+k KM since then) and I am not aware of its history.
About the sensors – yes I used direct fit OEM Bosch sensors.
I forgot to mention that there was a whistling sound from the flame trap so I replaced the nipple, bushing, o-ring and the flame trap (OEM again). I also checked the hoses for cracks/breakage. Today I noticed that I have some smoke coming out of the oil dip stick pipe when I rev the engine. This might be related to the emissions and that P0133 DTC. I am very thankful for every suggestion you may have.
BTW, I need to pass emission test ASAP because my license plate sticker has expired and I cannot renew it. Do you think some (or a lot) methanol (gas line antifreeze) in the tank will help with the emissions?

 

I would first replace distributor cap, rotor & ignition wires. This does not guarantee that you'll pass the emissions test, but your car needs them very soon anyway.

As to smoke coming out of the dipstick tube, it is a classic sign of retiring PCV components and it may be affecting the CO level (CO level also increases with lack of oxygen) so I would go ahead and replace the entire component as a kit. I am not sure what parts vendors are available in Canada, but in the U.S there are 2 I know of and some of us here have been using them:

http://www.fcpgroton.com/volvo850oiltrapturbo.htm
http://www.eeuroparts.com/info.aspx?type=terms

I am not sure if dry gas (gas line antifreeze) would reduce the amount of CO as I never tried it myself. But I would try dumping a large bottle of Techron fuel system cleaner into a half-filled tank and drive until the tank is near empty.


JPN