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1977 Chevy Impala 350ci failed smog check tech says CO2 and O2 too high

1977 Chevy Impala 350ci First test ABORTED TEST REASON:SAMPLE DILUTION. The tailpipe was full of holes. I replaced cat converter middle pipe,muffler and tailpipe, all new. It was all original and bad! Went back...Technician tested car off the rollers and said CO2% and O2% are not right and if I put this car on the rollers it will fail. At the passing test 2 yrs. ago, it was 11.4 %CO2 and 5.2%02 at 1300RPM. This time it was around 8% each. This engine is in restored condition and idles smoothly and runs like a top. I said, There are no maximum or minimum limits on these two! The pollutants are HC, CO%, and NO, not CO2% and O2%. If I test for them,this car will not pass. Is this technician right or wrong about this. I am going to change the spark plugs now. Please email ASAP, I only have until Monday 8/16/10. dandpt90@yahoo.com
Answer:

8% oxygen is in fact very high and does show dilution. Unless there is a dead cylinder pumping oxygen through the engine, somewhere within the exhaust stream oxygen is being added. Either way, I can recommend you have your Chevy smog check on a dyno to get actual HC, CO and NOx results; which ARE the emissions which will decide whether your 1977 Impala passes or fails the smog inspection. The smog tech is correct however; if he or she can not get the smog inspection to proceed because of dilution, there is no way of knowing the rest of the emissions test results. posted by SmogTips Support

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