1998 s70 emission failure

Aamazze · Post by **Aamazze** » 30 Aug 2015, 18:43

Please help , before I run my beloved s70 into a brick wall.
Let me start with a little back round.
Redid the head about two years ago . The car now has 235,000 miles on it. Brand new suspension ( front end ) about 2 months old. Replaced the MAF , O2 (front and back) , new temp sensor, cap and rotor , New gas cap ,plug wires , used smog pump , egr valve , fresh oil change , new vacuum lines and lastly , I did a sea foam treatment about mid June and again 2weeks ago.
I know that engine back to front. I'm a woman but know that car inside and out. I helped rebuild it. I love it. I don't want to have a car payment or give up my Volvo. I smoged the car twice so far and was surprised it failed. First reading (June ) % HC 66 %CO 0.22 %NO 749 at 15 miles
50 0.08 615 at 25 mph
So after I failed hc and no I did some work. Seafoam , oil change ,new gas cap , and did retest mid July .
Everything was improved ( can't find the numbers) but was in single digits as well. Seafoam made a believer out of me. NO was one point under failure at 25 mph at 716 passing but at 15 mph it went up. The smog tech told me that my cat was fine because of the numbers and to replace the O2 sensors.

Back to work. This is when I changed the O2 , temp , spark plugs , rotor , cap etc!
Today was another fifty bucks and these numbers % HC 17 % CO 0.02 %NO 3191 ( that no type o)
14 0.01 3511 at 25 mph
These numbers have tripled !

I am pleased to have the other numbers go down but am at my wits end with the NOX !!!!!!

Please help
Thanks in advance
Josephine Mazzeo

Post by **abscate** » 30 Aug 2015, 19:01

Welcome JM. It's great to see people keeping these cars alive, and we try to keep these Fora both nooB and female friendly.

I'm not an expert on smogging, since we don't have it here I NY, but did you notice your CO values plummeted when your NOX value skyrocketed? That's indicative of very lean mixture which is almost always caused by a vacuum leak. You have a bad hose, PCv, or intake manifold leaking in air where it shouldn't.

Aamazze · Post by **Aamazze** » 30 Aug 2015, 19:35

Any suggestions where to start. I did the PVC system in early February . Replaced most of vacuum lines and elbows . Do you have any idea why those numbers would triple ? Did I do something wrong ? Hook something up backwards? I was on my own today . No supervision . Lol JM

Post by **abscate** » 31 Aug 2015, 02:56

It's tough love but something is leaking somewhere. There is a vacuum elbow under the intake manifold that is notorious for tearing. The brake booster could be leaking in air ( does your brake pedal felt any different?)

Get a picture of your vacuum hose diagram, print it out, and systemically inspect every hose on each end and in between. ...VAT....visually, auditory, tactile.

After a PCv job, it's Often a challenge to get the intake manifold seated right or the new gasket just right...that would also male high NOX.

Aamazze · Post by **Aamazze** » 09 Sep 2015, 11:43

My honey ran into a Volvo guy at the parts store and mentioned to him about replacing the O2sensors and the gent told him that they had better be oem or the car might reject them and give crazy readings. Suggested we clean the old ones and put them back on the car. Is this a good idea?

Post by **abscate** » 10 Sep 2015, 00:51

we do have a lot of reports of problems with generic, off brand, or counterfeit Bosch O2 sensors

O2 sensors usually last about 100k at which point the electrochemical cell response gets sluggish, it can't really be cleaned. If they get dirty from oil , coolant, or excess fuel in the exhaust it might help.

I still think you are seeking a loose split or holed hose somewhere in your car.