In BC we have to have our cars emission tested (Cash cow for the governnment but thats another story) and my 1988 turbo 740 wagon failed. The things I have failed on are as follows.

Max allowed Hydrocarbons 95.00, my reading is 113.00

Max allowed Oxides of Nitrogen (NOx) 1052, my reading was 1690

According to last years report (from previous owner) it passed pretty easily, but than thats over a year ago already. What do you think it could be? I guess maybe its a few different things. I know this is kind of a long shot, but thought maybe someone out there might know. Thanks for any help.

We replaced the catalytic converter and that seemed to do the trick. Now the readings were really low, car is super clean now. The cat is an aftermarket one (made in Canada) and got for only $150. We also had changed the spark plugs. Thanks for your help.
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1988 745 Turbo

My car also failed aircare. My mechanic told me to drive on the highway to the border and back approximately 45 minutes of driving. I returned to the Richmond air care center. I was instructed by my mechanic not to turn the engine off and to rev the engine around 2500 RPM's while waiting to have the car tested.

The car was tested again and passed. My mechanic saved me some dollars.
Good luck!

don't rev it if you have a ZF tranny.
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Kenric Tam
1990 Volvo 740 base sedan (B230F)
My Volvo 'Project'

How do I know if its a ZF? I have an automatic 4sp in my 88 745t.

Hydrocarbons are unburnt fuel. I vote for a good tune-up and elimination of all vacuum leaks, as has been said. You can check the O2 sensor per the FAQ.

It is the cat's job to convert a multitude of polutants into Oxides of Nitrogen. I vote for a new cat, too. Good luck.

Correction:
I think that should be "converts Oxides of Nitrogen into CO2 and water vapor!!!"

Give it a tune up and set the basic idle speed and mixture. There is information in the 700/900 FAQ on this. If that doesn't do it, retard the initial timing about 5 degrees (no more than 10 degrees) and try again. No, it is not legal to re-adjust the car after passing the emission test.

I had the same problem in Texas a couple of months ago although my hydrocarbons were in spec, the NOX was probably close to yours. I replaced the O2 sensor ($115) and it had ery little effect. At first I didn't believe it was the catalytic converter because it was only a couple of years old. To make a long story short after I replaced the cat my NOX readings were about 1/2 of the limit.

Hope this helps

1990 740 220k

How much is a catalytic coverter worth? Can an EGR valve also affect readings?

I think I paid about US $ 150 or a little less for the cat and on the 1990 volvo 740 2.3 liter I have there is no EGR. You may be able to get the cat a little cheaper i didnt really shop around,.

Good Luck!

Hign NOX is usually caused by vacuum leaks. Check hoses and injector seals. Check the FAQ for more info.

Try a complete tume up.
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Warren Bain - '86 744Ti M46 >290Kmi, '99 V70Glt > 45K mi, '96 965 >100Kmi Wifemobile near Manassas Va.. Check the 700/900 FAQ via the 'features' pull down menu.

o2 sensor?
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Kenric Tam
1990 Volvo 740 base sedan (B230F)
My Volvo 'Project'