My cousin has a 92 isuzu rodeo (v6) that failed the california emissions test in the NO reading. The numbers were a bit worse at the low speed reading than the higher speed check. What should be checked under the hood . The cat was replaced a couple of yrs ago with a generic cat.
Thanks in advance Pat
Well when I check Nox I check 3 basic things. First I see if the EGR valve is working. Pumping up EGR with a vacuum pump should stall or make the engine run rough at idle. Also check vacuum going to EGR valve, maybe a good manual wil tell you the details. Also sometimes the oxygen sensor doesn't cycle fast enough to keep cat supplied with CO (carbon monoxide) hook up an oscilloscope to oxygen sensor and run in park at 2000 rpm it should cycle at least about 2 to 5 times a second. This will usually cause a small amount of Nox not a large. And lastly generic cats sometimes only last a year or two or less. This is my bet the cat needs to be replaced. Just saw a 92 toyota camry where owner had a 90 dollar cat installed about a year ago and he bought a 150 cat and passed nox.
The check engine light is not on?
Professor
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