Won't pass emissions -- any ideas?
08-23-2002 | 10:28 PM
#1
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From: Seattle
Won't pass emissions -- any ideas?
I have a modded 78 930 in Washington that needs to pass smog one more time before it becomes exempt. It passed comfortably in all categories (HC, CO, CO+CO2, and O2) at cruise, but failed in one category (HC) at idle (allowable limit is 600 PPM, mine was 1143 PPM). Their generic chart suggests that excess unburned fuel is the cause (makes sense), and that possible causes include "mechanical/electrical failures, vacuum leaks, or a very lean air/fuel mixture." Does anyone have any suggestions on the most expedient way to bring this thing into compliance, even if only temporarily?
08-23-2002 | 11:11 PM
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From: San Francisco
Those numbers at cruise indicate a lean misfire. First have your air/fuel mixture checked out - It might be too lean. The mixture adjustment screw is on top of the fuel distributor and requires a short 3mm. alan wrench; small turns (I mean less than an eighth of a full turn) equal big results. Turn clockwise to richen. If it is not a fuel problem it may be an ignition problem such as weak spark to cyl.
08-24-2002 | 01:55 AM
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From: Seattle
Thanks for your thoughts. The problem is not at cruise -- at cruise, the HC is fine and CO is 2.6%. The problem is with HC at idle. Do you think I should richen it to achieve better results at idle? I'm concerned I'll blow past the limits at cruise if I do that. I don't think I have a misfire, though with the 964 cams, the idle is a bit lumpy. The engine is twin plugged, with Bosch W3DPO plugs gapped to .032, Magnecor wires, fired by an Electomotive TEC-1. I don't detect a misfire at idle, but the engine doesn't really sound all that happy idling, which I attribute to the cams, but I'm not sure. Any other ideas?
08-24-2002 | 02:32 AM
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From: San Francisco
My mistake, I wanted to say the numbers at idle indicate a lean misfire. Then again I only had one gas reading. If you give me all the gas values at cruise and idle I will be able to help you a lot better. Please let me know if the emissions test was run on a dyno and if the car has a convertor on it. I have repaired many failed vehicles doing smog testing for so many years. You can also e-mail me at mstrtek@netzero.net or call me.650-992-0978