Tsullappliance Posted November 13, 2005 Share Posted November 13, 2005 Hi everyone. Thanks for reading this. My '87 Gl 2bbl has a high CO% reading. In the state of Virginia we must have the tailpipe emissions checked every two years in some countys.Is there a way to adjust the air/fuel mixture so it doesn't run so rich? The car passed at 25mph but not at 15mph. Any help would be greatly appreciated. Quote Link to comment Share on other sites More sharing options...
Subarian Posted November 13, 2005 Share Posted November 13, 2005 I finally got rid of my stock carb and got a Weber because I couldn't get the stock Hitachi to pass emissions. But if you don't want to do that , you can add denatured alchohol to your tank. About 1 gallon to 5 should guarantee you pass. Quote Link to comment Share on other sites More sharing options...
kayakertom Posted November 13, 2005 Share Posted November 13, 2005 There is an angled air/fuel adjusting screw on the right side (facing the engine from the front of the car) of the Hitachi carb, but unless you have a meter or have done it before, I'd leave it alone. New NGK sparkplugs and a can a seafoam in the gastank and a little bit of highway driving before retesting may get you through. Quote Link to comment Share on other sites More sharing options...
Tsullappliance Posted November 13, 2005 Author Share Posted November 13, 2005 I finally got rid of my stock carb and got a Weber because I couldn't get the stock Hitachi to pass emissions. But if you don't want to do that , you can add denatured alchohol to your tank. About 1 gallon to 5 should guarantee you pass. Thanks, I'll let you know how it turns out. Can't swing the carb before the end of the month so I'll try the the alcohol. Quote Link to comment Share on other sites More sharing options...
Tsullappliance Posted November 13, 2005 Author Share Posted November 13, 2005 There is an angled air/fuel adjusting screw on the right side (facing the engine from the front of the car) of the Hitachi carb, but unless you have a meter or have done it before, I'd leave it alone. New NGK sparkplugs and a can a seafoam in the gastank and a little bit of highway driving before retesting may get you through. When you say meter, do you mean a vacuum gauge of some sort? If so, would the highest vacuum mean the best mixture? I've balanced carbs on other makes but they had two or three carbs and could be very tempermental. I will change the plugs and the PCV today and let you know how it works out. Thanks again! Quote Link to comment Share on other sites More sharing options...
rubuild Posted November 13, 2005 Share Posted November 13, 2005 I've seen this problem a number of times, and found it to be an aftermarket PCV Valve, or an air control valve with oil in it. The PCV Valve was the most common, the OEM valve will have a 31D (or the like) stamped on the hex part of the valve and an oem will say made in USA (bless their souls) where the hose fits on on most. Kerry/Roo-Builders Quote Link to comment Share on other sites More sharing options...
GLCraig Posted November 13, 2005 Share Posted November 13, 2005 It would help a lot if you could post your emission test results, so we could give better advice. Quote Link to comment Share on other sites More sharing options...
Tsullappliance Posted November 14, 2005 Author Share Posted November 14, 2005 It would help a lot if you could post your emission test results, so we could give better advice. Sorry about that: HC ppm 20 with 216 as the limit. CO% 3.19 with 1.84 as the limit. NO ppm 6 with 3135 as the limit. These were all at 15mph. When the mph was brought up to 25mph the Co% dropped to 2.16 with 2.39 as the limit. NO ppm dropped to zero at 25mph and HC ppm went to 23 with 210 as the limit. I did replace the PCV valve and plugs (two carbon fouled) this weekend and cleaned the cap electrodes and rotor. Was going to replace the cap and rotor but they gave me the wrong parts.The air filter was changed also. The plugs I put in were NGK BPR6ES-11. I also sealed each end of the plug wires with di-electric grease. The oil and filter were changed last weekend and the exhaust is brand new, including the cat. From what the previous owner told me, this CO problem has persisted for a number of years and his mechanic would tweak something to get it to pass.The plugs were gapped to .044 and needless to say the car has much better pick-up. The carb adjustment has me puzzled in that you have to back out the mixture screw quite a ways to get the engine perfectly smooth. One more thing, I did replace some brittle and cracked vacuum hoses including the one to the PCV valve. Hope I didn't bore you to tears with too much information.The tune-up work was done after the test, so who knows. Maybe it will pass now. Im going to replace the air control vacuum valve and the bowl vent vacuum valve before bringing it back. At thirty dollars a pop these damn tests get expensive! I wish you could test it before going back to the shop. Tom Quote Link to comment Share on other sites More sharing options...
hatchsub Posted November 14, 2005 Share Posted November 14, 2005 Does this car have an O2 sensor? If so you might want to think about replacing that. My car had a high CO% and failed until i had the O2 sensor replaced. Then it passed without a problem. Quote Link to comment Share on other sites More sharing options...
Tsullappliance Posted November 14, 2005 Author Share Posted November 14, 2005 Does this car have an O2 sensor? If so you might want to think about replacing that. My car had a high CO% and failed until i had the O2 sensor replaced. Then it passed without a problem. No O2 sensor Quote Link to comment Share on other sites More sharing options...
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