Exhaust leaks

[billr]

OldNuc has mentioned, many times, how important it is to eliminate exhaust leaks when trying to pass smog testing. Here is a recent example of how crucial that can be:

I took my '95 SL2 (CA emissions, electric EGR) in Tues. and it was very clean on everything but NOX at 25 mph. That was a whopping 841 ppm with the max allowable being 774 and "average" being 270. Even the NOX at 15 mph was low, only 27 ppm. So, I took it home and hooked up a blower to the tailpipe and found a leak at the gasket between the exhaust manifold and down-pipe. I sealed that and took it back for testing today with no other changes. The NOX at 25 mph is now 6, and at 15 mph it dropped to 5. This engine is an "oil burner" with 260K miles.

PS: I just noticed that the HC about doubled when the leak was fixed; still well under even the "average", though. CO remained the same at .01%

[focusofheart]

Thank you for the information.

My Saturn failed the test (CA) on Monday due to the HC being 71 (15mph) so the spark plugs and wires were changed out and the HC lowered to 54 so she passed.

My NO dropped after the change in plugs from 61 to 37, so maybe I should have my exhaust inspected for any small leak, just in case.

My Saturn had 218,121 at the time of the test.