GarageRatt13 Posted March 19, 2012 Share Posted March 19, 2012 Well just as the title says my 73 240Z is sputtering at idle. But if you bring it to 1000 rpms or above its smooth. When i got the car last week it had old gas in it so i drained it and put new gas in. Do you think it still has some old gas in the system? Any ideas would be great. Thanks. Quote Link to comment Share on other sites More sharing options...
neotech84 Posted March 19, 2012 Share Posted March 19, 2012 Check your carbs out. I bet a good tune will solve this problem. Quote Link to comment Share on other sites More sharing options...
GarageRatt13 Posted March 20, 2012 Author Share Posted March 20, 2012 i'll check into it this weekend, thanks. Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted March 20, 2012 Share Posted March 20, 2012 (edited) Increasing rpm may only be masking the miss. Check fuel, spark and air: in that order. Don't worry about air - I 've never seen a dirty air filter stop a car from running (although it may for off-road vehicles where things get REALLY dusty). If the car ran before, the last thing I would do is adjust the carbs (you can open up a huge can of worms "adjusting" a carb that is not the actual problem. Check fuel filter and banjo fittings on each carb. I find a cheap fuel pressure gauge VERY helpful in trouble shooting. Install it in the flex line leading to the carbs away from anything that can break it - you are looking at about $200 and it will work for years. I learned to carry a few fuel filters and a screw driver in my glove box. If car started sputting or died, I'd look for zero fuel pressure, then a new fuel filter would almost always get me home. Got to be such a problem that I had to carry some compressed air to blow the crap out of the solid fuel lines and back into the fuel tank, where it stayed for a while, but soon stranded me again. A re-built fuel tank finally got me some sanity. I have already used a fuel pressure gauge to help me find the problem on my new LS2 (clogged fuel filter)-without the gauge, I'd have gone thru the whole ignition system for no reason at all. These old cars get old rust, varnish and algae in the tank. This stuff will look like rust or red-clay mud in a paper filter and if it gets past your fuel filter it will look like little rock fragments in the banjo fittings. When I used to clog a filter, for some reason it was almost always right after adding fuel to the tank, maybe it aggitates the sediment or water in the bottom of the tank. Check your distributor cap and Sand off any scorched places and inspect the "button" in the distributor cap to make sure the spring under it still works and make sure the cap has no cracks. While you are checking the fuel filters, look for corrosion on distributor rotor and button, clean contacts with fine sand paper or a pencil eraser, ensure distributor cap has no water (condensation) inside of it and replace it. Pull out plugs and look for fouling, then pull one plug wire off at a time and see which one fails to reduce your rpm (that is the bad wire). Ensure plug wires snap on firmly. Your maintenance manual may be able to tell you how much resistance your plug wires should have, and perhaps you can check that with a voltmeter. Make sure none of your plug wires are touching each other direcctly (cross fire). Draining the gas does not clean sediment out of the tank-the drain hole is in a flat section of the tank. The draining may have just pulled more crap closer to your fuel pick-up hose. Good luck. Edited March 20, 2012 by RebekahsZ Quote Link to comment Share on other sites More sharing options...
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