Failed Emissions Test in Chicago, IL area

[Buick in Olds]

Have an 84 Olds Cutlass Supreme with a 3.8L. The motor was a new GM rebuild. Pulled stock cam and installed one from Lazer Cams. Intake was replaced with a 4.1L and the stock Quadrajet was rebuilt by a local mechanic. The CAT is the old one that was on the car before rebuild, am running duals from the CAT back. Stock HEI with exception of a hotter coil from Mallory. Did not reinstall the air pump and plugged the fitting on the CAT.

Took the car in for emmisions test today and it failed. The readings were:

HC - Me 2.10 / Standard 2.0
CO - Me 57.2 / Standard 30.0
CO2 - Me 471.5 / Standard N/A

Test type is IM240 run on a DYNO. Waited in line 20 minutes before test.

Any suggestions to improve test results.

 

[jiho2]

Uh, how'd you get through smog without a smog pump?

Anyway, your dual-bed cat needs that smog pump, the fitting you plugged feeds air to the rear bed so it can burn the HC and CO that you failed on the test.

I do think that's where I'd start....

-- Jim Howard <jiho@c-zone.net>

 

[b4black]

I passed in Chicago without an AIR pump, but I had a brand new converter designed not to use an AIR tube.

I'd either put the pump back on, or get a better converter.

 

[jiho2]

Originally posted by b4black
I passed in Chicago without an AIR pump, but I had a brand new converter designed not to use an AIR tube.

I'd either put the pump back on, or get a better converter.

Sheeze....here in California, tampering rules flunk you up front without a smog pump. But if you can get away with it and don't care what your car does to the enviornment during warmup....

Just to be finicky: The computer in the '84 Olds doesn't twiddle the mixture -- rich for the reduction phase, lean for the oxidation phase -- the way earlier computers for monolithic cats do. It tries to get ideal mixture all the time, which favors the reduction phase (NOx), and lets the smog pump drive the oxidation phase (HC and CO). So without a smog pump, it won't matter whether he has dual-bed or monolithic, either way the oxidation phase will be starved. A new cat of either type would probably offer a similar (small) improvement.

On the other hand, with his carb tweaked nicely maybe it wouldn't matter as much anyway. That may be what he's really after, and I have no wisdom for that....

-- Jim Howard <jiho@c-zone.net>