Yo guys, I need some help please. My 88 IROC failed the California smog test. I live in one of those counties that requires the chassis dyno test, where the engine is tested under load at 15 and 25 mph. It failed the tailpipe emissions sniffer test at both speeds. I had HC, CO and NOx over the max limits in all cases. The guy who did the test suggested that I replace the O2 sensor and the EGR valve, and install a new cat. But the cat on the car now is only 3 yars old! He told me that aftermarket cats are NFG, and I should get one from GM.

One strange thing I noticed during the test, is they ran both speed tests with the transmission in 2nd gear (I have the T5 tranny). Now maybe 2nd is fine for 15 mph, but at 25 mph the engine was turning close to 2400 rpm. I never drive 25 in 2nd gear, I'm usually in 3rd or maybe even 4th at 25 mph. Could the high engine rpm on the 25 mph test have caused me to fail?

Anyway, I just put in a new O2 sensor, that was easy, took 5 minutes. But the EGR valve looks like it's buried inside the TPI plumbing. How do you get to the thing in order to replace it? And what about the EGR solenoid? Does it need to be replaced as well?

Thanks!

 

You must drive like grandma if you're in 3rd or 4th at 25 mph. The old smog test before the dyno, they would test at idle and about 2500 rpm. Your 3 year old cat might have been trashed by that bad O2 sensor letting the engine run rich. As far as the EGR goes, I've never done one on a TPI engine but my guess is you have to remove everything that's in the way