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[TroyDest]

In my '82 931, I've failed two smog tests in the last few months. I'm trying to get it to pass so I can register it. I'm in California by the way!

This last time, it had high NOx and CO which the mechanic claimed was an indication of running rich.

The time previous (with a big vacuum leak), it had high NOx and HC.

In both cases, the mecanics said high NOx was from carbon deposits in the combustion chambers and there wasn't much you could do about it short of pulling the head and cleaning it. Does this sound right to you guys? I'm not real familiar with NOx.

I've heard of chemical solutions out there that clean up the combustion chambers. Has anybody had any luck with them?

Thanks for any help guys. -Troy

[numbers]

No, it doesn't sound right. These cars run really clean unless they are way out of ajustment. Check all of your vacuum lines again. Pay particular attention to the elboe's on the vacumm pipe. They tend to crack along the bottom where you can't see it. Once you are sure that you have no vacuum leaks, re-adjust your fuel mixture. Change the oxygen sensor, and replace your oil with Mobil-1(recommend 15 W-50 for the turbo. Install new spark plugs, and check/set engine timing. It should pass easily.

[larso]

Bad gas causes the spark plugs to foul up with black. Check your spark plugs. If your mixture is set right, and it's still black, the gas is bad. Drivign the car to an almost empty tank and refilling won't work. And that also will kill your fuel pump, so it's best to drain it all out and somehow clean it. I don't know how. You can put that watter eater stuff in the gas to clear some of it out.

[larso]

BTW when i had bad gas in my old 931, I started it up on the last 4 litres of gas in the tank and my back yard was BLACK, and the neighborhood smelled as if 7,000,000 people were running there snow blowers all at the same time.