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Discussion Starter · #1 ·
I have a '83 280ZX that failed emissions, the test is done at idle and at speed. The
readings are HC 495 (limit 167) and CO 8.11 (limit .94) The car has 146,000 miles on it and has the original catalic converter. This is the first time the car was tested at speed. Any information would be appreciated. Thank you

John
 
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Before I jumped into anything, the first thing I would do is replace the cat. You can get a generic one for $100 or a high performance one for $150. Also, when you take your car down for testing make sure it is good and hot. If it is possible, ask the guy for an appointment and then run the car up and down the highway and bring it directly in for the test. The hotter that cat is the better the readings should be if the only problem was the cat. Good luck. John
 

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JML's advice is good. That's exactly what I do.

I can't really "read" what bad emissions numbers mean. But if I fail, I ask the guy what I need to do. My mechanic is really good about telling me. Just this year, my wife's car wouldn't pass as it has blowby (a Chev S-10 Blazer, what a POS) and all that oil eventually kills the cat. He said with a new cat, the car would probably pass with flying colors — and it did.

Also, you don't mention what state you're in, but in CA, they let you do a 'pre-test'. For $20 (half the fee for the full test), they'll run the car through and tell you whether it will pass or not — off the record. If you don't do that, and your car fails badly, it will be classified as a gross polluter, which is the DMV equivalent of being branded a child rapist.

Otherwise, just make sure the car is up to spec on timing, idle speed, plug gap,etc. before you bring it in.
 

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I did exactly what JML recommends plus the following:

Set the idle as close to 1200 RPMs without going over.
(Any inspection station technician will tell you what the
maximum setting is, if it is different in your state).
You will have to set it before you get there. The tech.
is not allowed to let you do anything to the car when you
go for the test.

I poured a can of additive for smog test by CRC from Checker
Auto Parts Store, filled the tank with fuel, drove it until
it was almost empty, and then refilled it. Drove like ****
for about an hour which was difficult to do in the morning
traffic. I drove it like this the next morning before the
station that I had chosen to take it to opened. I wanted to
be the first there. While waiting for it to open, I rode
accellerator off and on and when the technician arrived, I
just let it idle at 1200 RPMs as I had previously set it. I
did not turn the engine off at all.

Thanks to all the people on this site who helped me get through
it. Good Luck, Ernest Las Vegas, NV
 

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In CA you can't have your idle above spec by more than 100rpm.

Mine failed as a gross polluter last time and adjusting the AFM internally did the trick. There are procedures posted for how to do it. With numbers that high, it is running awfully rich. I don't think it is just the cat with numbers that high though.

good luck
 
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