aznguy888

I have a 92 B4C and I live in Denver. Someone told me to advance the timing 1 degree per 1000 ft above sea level so I have it at 11, but it recently failed emissions with high CO, NOX, and HC. I have new plugs, wires, cap, rotor, O2, MAP, TPS(although I haven't adjusted TPS yet), ECM, PROM or EPROM(It cost like $500), fuel pump, fuel pump relay. The cats were checked and the dude told me they were alright, but it runs rich, you can smell it. Anybody have any ideas on how I can pass emissions?

1987IROC350

How bas did it fail? Post the passing vs. your readings. There is a product you put in the fuel that might help you if the reading are not incredibly high.

Would getting the test run at lower altitudes help?

I failed recently but my motor was not broken in yet. So I registered the car in a County down from mine that does not require an emmision test. I only changed the "Garage location" of the car on a DMV form. Very easy to do here. I couldn't believe it was legal.

But I'm sure you want to fix the rich prob. I had a BBK adj. fuel pressure reg. installed and that fixed my issue. It seems to runs great now.

Gord's Green Z28

Did you ever get this resolved? I drove through Colorado (Wyoming to New Mexico) at 8° timing with no problems whatsoever. I've since bumped it down to the stock 6°.

I've heard of different octane levels at altitude. But never timing before. One thing I do know from adjusting timing is that a small change makes a huge difference in drivability. I can't imagine driving my car at 11°. It would ping like crazy. But then again, I'm at sea level.

The idea makes sense though. A bit less oxygen in the air high up in Colorado. Give it a bit extra time by upping the timing. But I'd try 8° and get it tested. 8° in CO should be like 6° anywhere else. Possibly 9°, but don't get too crazy.

wulff82

I went through the same thing, I lived in colorado for most my life and getting my 87 iroc to pass was rough.... The basic stuff sounds like it's already done, but that tps sensor will make a big difference.... Put it as low as possible with still maintaining an idle... maybe .052 it should be more like .056 normally.... This will lower your co fast.... The other little trick is to cut a hole in the pipe right after it comes out of the muffler but before the tip, it won't be much louder and it won't go in the tale reader as much.... but that's only if your desperate.... The way it's driven on the dyno is very important...if they have a heavy foot it will make it run higher. Good luck, thanks for reading my 2 cents