1998 S70 Volvo Non-Turbo Not passing smog

fixitmyself · Post by **fixitmyself** » 27 Aug 2010, 15:58

So, I have never had a problem with my car passing smog until now.

1998 S70 Sedan Non-Turbo

According to the smog tech everything passed but the NO (PPM) was high. The measure was 722 and he said it was running way to hot. Anyone have an idea what is the issue? Thanks for any help.

Hope non-turbo answers the trim. Sorry I could find an answer. If you need any more info please let me know.

fixitmyself · Post by **fixitmyself** » 27 Aug 2010, 16:30

Sorry, I have 195,000 miles on the car.

Post by **jdw** » 27 Aug 2010, 18:32

The high NOx problem on my 850 n/a was caused by a bad SAS valve which caused a vacuum leak. I would check for vacuum leaks in general.

Fixing it also brought my cruise control back to life. Not sure if that was related.

Post by **jblackburn** » 27 Aug 2010, 18:35

+1, I would check for vacuum leaks. A can of carb cleaner sprayed around any vacuum lines you can find will give you a surge in engine speed if there is a leak there.

I might, at this mileage, suspect your PCV is clogged, or the vacuum line on that system (to the left side of the intake manifold) is cracked.

850tech · Post by **850tech** » 27 Aug 2010, 19:07

Agreed, start with vacuum leaks as this is a vary common failure on these cars and a lean A/F ratio will drive combustion chamber temps way up and NOx will increase.

One thing I need you to clear up for us is the comments about the car running way to hot. Is it overheating or running any hotter then it has in the past? If so this is where you need to start. NOx forms in excessivly high combustion chamber temps, and a malfunctioning cooling system = abnormally high temps.

Other likely causes include, a faulty EGR (if equipped), O2 sensor stuck lean, poor fuel pressure, exhaust leaks pre-cat, carbon build up, or a failed converter. eliminate the cooling system and vacuum leaks first then if your still having issues, diagnose the above in that order. Do the converter last as converters usually don't just die, they're murdered. 90+% of converter failures are cause by faults in the A/F ratio or engine so not fixing the source of the converter failure is a real waste of money.

fixitmyself · Post by **fixitmyself** » 01 Sep 2010, 15:24

Thank for all your help I will be moving forward with your advice.

The car is not overheating though. It was just mentioned to me by the smog tech that it was running hot. Not exactly sure what he means to be honest.

Thanks again.

Post by **polskamafia mjl** » 01 Sep 2010, 16:25

He means the combustion temperatures are higher than normal.