whyrualive Posted June 18, 2007 Share Posted June 18, 2007 My 72 240z went down in flames during the emission test. The first problem I had was getting the RPM's below 1350. When the results came back, the CO2 was off the chart 9.99% and the HC were 1241 (range 750-1000). Then on the way back, it died everytime I took load off the engine (i.e. stoplights) unless I kept the RPM's at 3000. Ahhhh! I suppose that I need to tune / rebuild the carbs, but what else do you suggest? Quote Link to comment Share on other sites More sharing options...
randy 77zt Posted June 18, 2007 Share Posted June 18, 2007 look up z therapy for carb kits and throttle shaft kits.make sure any vacuem diaphragm operated parts(distributor advance,smog pump diverter valve)and leaking internally-think hole in diaphragm.check distributor for wear and advance curve.the idea is to get the car operating in as new condition.many things can be wrong in older car. Quote Link to comment Share on other sites More sharing options...
SHO-Z Posted June 19, 2007 Share Posted June 19, 2007 From what I have researched if the carbs are tuned right the cause for high HC is weak ignition. I have read that using a multi spark ignition will solve most HC problems. I would go thru the carbs first and then do the ignition. Quote Link to comment Share on other sites More sharing options...
280zwitha383 Posted June 19, 2007 Share Posted June 19, 2007 I know you have more involved problems so this probably isn't for you, but what about that additive that guarantees to pass emissions test. Does that stuff work (without killing anything)? Quote Link to comment Share on other sites More sharing options...
whyrualive Posted June 19, 2007 Author Share Posted June 19, 2007 I appreciate the advise. I'm going to take the advise and get the carb rebuild kit, change the plugs, wires, cap, rotor, adjust the valves and give it a try. If that doesn't work, I'll upgrade to an electronic ignition. If that doesn't work, I'll expedite my L28ET upgrade and try again. Quote Link to comment Share on other sites More sharing options...
Austenp405 Posted June 19, 2007 Share Posted June 19, 2007 That's an easy fix. Get a PO Box in a county that doesn't require emissions tests and register it there. Not that I advocate such a thing... As for fixing the driveability problems, not a clue. Quote Link to comment Share on other sites More sharing options...
CArFAn Posted June 19, 2007 Share Posted June 19, 2007 i thought you didnt have to have cars pre-1975 do that test... just get the head lamp and brake check is what i was told Quote Link to comment Share on other sites More sharing options...
randy 77zt Posted June 19, 2007 Share Posted June 19, 2007 in some areas that dont meet federal air standards cars have to be smogged-and they are just as strict as california.reno and denver are such places.some places only look at emissions though-if you can make it better with aftermarket parts they allow them. Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted June 19, 2007 Share Posted June 19, 2007 High HC can mean it is running too lean. When I had to smog test my 70 I found the tune that returned the lowest emmissions was also the tune that made it run the best. If your car is in reasonably good shape you shouldn't have any problem passing smog. The requirements on these old cars isn't that tough. Whatever you do save the reciepts for the parts you put on. There is a dollar limit on what you have to spend before they give you an exemption. My guess is the price of the carbs will be enough to give you the expemption. But I wouldn't give up there. If your car is relatively stock and isn't passing smog then it isn't running right. You inability to idle suggests a vacuum leak to me. As bad as it sounds you might have a disconnected or broken vacuum hose. That could also be causing the high emmisions. Quote Link to comment Share on other sites More sharing options...
whyrualive Posted June 19, 2007 Author Share Posted June 19, 2007 High HC can mean it is running too lean. When I had to smog test my 70 I found the tune that returned the lowest emmissions was also the tune that made it run the best. If your car is in reasonably good shape you shouldn't have any problem passing smog. The requirements on these old cars isn't that tough. Whatever you do save the reciepts for the parts you put on. There is a dollar limit on what you have to spend before they give you an exemption. My guess is the price of the carbs will be enough to give you the expemption. But I wouldn't give up there. If your car is relatively stock and isn't passing smog then it isn't running right. You inability to idle suggests a vacuum leak to me. As bad as it sounds you might have a disconnected or broken vacuum hose. That could also be causing the high emmisions. While this is frustrating and will cost a few bucks, I want the car purring like a kitten. Right now it is stressful to drive it and that isn't good. I think you might be right about the vacuum leak. While I'm at the store, I'm going to pick up some hose and replace them. Quote Link to comment Share on other sites More sharing options...
Hey_Allen Posted June 19, 2007 Share Posted June 19, 2007 I'd always seen that running lean gave high NOx, whereas high HC was unburned fuel running out the exhaust. Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted June 19, 2007 Share Posted June 19, 2007 I'd always seen that running lean gave high NOx, whereas high HC was unburned fuel running out the exhaust. Yeah, you're right. I was thinking high CO. But a vacuum leak is still a possible cause. Any way you look at it just basic tune up diligence should fix the issue. High HC emissions are caused by only one thing' date=' incomplete combustion, this could be due to an engine misfire, an intake air system leak, a burned valve or low cylinder compression on any of the cylinders. What this means is that the engine is not burning all of the fuel in the combustion chamber and expels most of the fuel out of the tailpipe without converting it into CO, which means there is a problem with one or more of the cylinders. It could be simply a bad spark plug or spark plug wire or a loss of engine compression in one or more of the cylinders, I recommend having the basic engine functions checked for a misfire condition [/quote'] High HC is due to misfire. Check the plugs and wires. Rich mixture wouldmake high CO and HC. This could also be caused by a lean misfire. Quote Link to comment Share on other sites More sharing options...
whyrualive Posted July 12, 2007 Author Share Posted July 12, 2007 I changed the plugs, rotor, and cap. No change - maybe it got worse. I purchased the carb tune-up kit from ZTherapy and will let you know if that works. Quote Link to comment Share on other sites More sharing options...
randy 77zt Posted July 12, 2007 Share Posted July 12, 2007 you will probably find the throttle shafts need to be rebuilt on the carbs.to sync the carbs i use a 3' piece of 5/32 vacuem line you stick 1 end in your ear and the other up to the bottem of the carb slide and listen to the sound of the air rushing through.use a mityvac and check the vacuem diaphram parts(distrubutor advance,air pump divertor valve) for leaks -these are usually ruptured on an old car and makes vacuem leaks.the carbs are really very simple-i had my own shop a few years back the specialized in z's.i built a few 240's with l28 bottem ends and 240 top ends-makes a nice simple car with a 82 or 83 non turbo trans. Quote Link to comment Share on other sites More sharing options...
big-phil Posted July 12, 2007 Share Posted July 12, 2007 Thats crazy, a car that old has to pass emissions? Quote Link to comment Share on other sites More sharing options...
Zmanco Posted July 12, 2007 Share Posted July 12, 2007 Whyrualive, when I brought my '73 to CO (still had 3 screw SUs then), i went to Bob Bush at Fortunate Wheelz in Lakewood. He tuned it for emissions and sent me about 2 miles down the road to an emissions tester. I passed there, drove back, and then we reset the tune so I could actually enjoy driving the car That won't solve any major issues such as worn throttle shafts, but it might just get you past this test and let you make any fixes more at your own pace. Quote Link to comment Share on other sites More sharing options...
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