Hi everyone,

First of all, I am a first-time poster on this message board. I love Volvo's - especially mine.

I own a 1988 740 GLE non-turbo. Recently, it failed its emission's inspection. Here are the stats:

HC (PPM)
15 mph MAX: 209 MEAS: 165
25 mph MAX: 194 MEAS: 169

CO (%)
15 mph MAX: 0.86 MEAS: 0.86
25 mph MAX: 0.76 MEAS: 0.86

NO (PPM)
15 mph MAX: 1791 MEAS: 2580
25 mph MAX: 1591 MEAS: 2473

The HC passed with flying colors. The CO barely failed. The real problem is the NO it seems. The one thing I did not do was get the car to the emissions inspection warm - it had been sitting for about 45 minutes before they tested it. However, when I lived in California, I went to a Volvo specialist who seemed to know exactly what to do to make my Volvo pass - and I do not remember what that was. So, I thought before I tried anything else I thought I would post on this board to see if anyone had any ideas.

I do not use premium gasoline. Will that help? Will it also help to replace the cat? I am not sold on this is as a solution because high NOx is the cause of high combustion temperature. Any help would be greatly appreciated.

Thanks,

Sandman

 

I would change the O2 sensor.....even though it doesnt show as a problem is could still be...cheap option to try.

over fueling could be the problem also...maybe timing..

just an opinion.....lets know what happened...thx

 

Lots of times high combustion temperatures are caused by a lean fuel/air mixture. Look and listen for air and vacuum leaks - intake and exhaust gaskets, split vacuum lines and bad injector seals. Look for holes in the large hose that connects the air mass meter to the throttle body.

 

exhaust leaks......I passed everything but the NO TEST....a smog dude told me exhaust leaks....I used the beige paste that you can smear on the joints through out the exhaust system....

cold exhaust
spread with a stick or latex glove and finger....
all connections where claps may be AND THE MUFFLER....
leave it for two hours and done....
drive to California and back to smog place...
finito

 

Assuming your timing is where it should be, 12 degrees BTDC, retard it to 6-8 BTDC...it'll pass. NOx is a result of higher than acceptable combustion temps; the usual places to check are bad catalytic converter and/or bad egr valve. It's quite possible the O2 is bad, people don't seem to get just how important they are...a bad O2 can cause the car to run rich, running rich screws your gas mileage and the extra fueling ruins your catalytic converter! And...leaks after the amm and before the tb can mess w/ things. But to pass, just retard the timing as mentioned. I had to do that every year on my 84 760T...works like a champ!

 

get the tank so it only has a few gallons of gas in it, put in a few bottle of dry gas and drive her over to the shop.

done. =)

That's a lot cheaper then an O2 sensor, and worth trying first.