1985 240 extremely high HC & CO readings. Failed Emissio

[johnny3000]

I just bought this 1985 240, and it has failed the emissions test.
Here are the readings.

25/25 test
HC ppm - reading 288 - allowed 162
CO % - reading 6.35 - allowed 1.04

50/15 test
HC ppm - reading 302 - allowed 167
CO % - reading 6.7 - allowed .94

everything else passed.

The car has new plugs, plug wires, distributor cap, 02 sensor, timing belt, all the other belts, water pump, oil and oil filter.
The timing was set by a volvo dealer I'm told, so that should be ok...It runs great. It starts right up, cold or warm, and idles fine. It doesn't noticably smoke either.

I have no idea where to look for the problem considering how well it runs. Any help will be greatly appreciated.
thanks,
j.j.
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[Kmaniac in California USA]

Now, I am know professional expert on this subject but here are my two cents. This such high HC readings, I would suspect a bad catalytic converter. These things tend to burn up, especially if the car was running poorly for a long time prior to your tune-up. Another thing you might want to try is disconnecting the wires to the Air Mass Meter on the intake hose. If the RPM's remain constant after you disconnect, you may have a faulty meter which is stuck in limp mode. Still another possibility is a faulty fuel pressure regulator, causing a slight increase in fuel mixture. Anyway, those are my thoughts. Happy troubleshooting.

[Kushball]

I also had the same exact problems and replaced all the electrical stuff too. Found out that it was a faulty catalytic converter. Replaced that and everything was smooth sailing.

[csbrianp1]

I would also try running hotter plugs. That's how I fixed my smog problem. Warning, go only 1 step hotter or you'll fail the NOX.

Brian