260ZRED Posted November 27, 2002 Share Posted November 27, 2002 Hi! Can anyone point me in the right direction? I have a 74 260Z with 2 round top SUs which really hesitates and begins to die at speeds greater then 50 MPH. The gas pedal just feels very weak and i can feel the whole engine choking itself to death. It even died a couple times on the freeway (scary!) I know that my valves really need an adjustment (they clang/click like crazy), I am working on that now. However, the car feels really strong at low speeds and I honestly have no idea what the problem is. Also, my gas tank has a small leak which stops once I have less then a half full tank. Every once in a while, everything works PERFECT, and I can go about 90mph with everything workoing fine. Of course, my electric fuel pump is on. The fuel filters look clean. And I have never messed with any carb settings because the car ran good. I am pretty new at this... if anyone has any help I would be gratefull!!! Quote Link to comment Share on other sites More sharing options...
260ZRED Posted November 28, 2002 Author Share Posted November 28, 2002 cmon guys... no one ever had this problem??? Quote Link to comment Share on other sites More sharing options...
Cody 82 ZXT Posted November 28, 2002 Share Posted November 28, 2002 What condition is the ignition system in? I would think that it's possible for the ignition system to not be able to keep up with the demand at higher RPM'S and load situations. Since you said that it works perfetly at some times it makes me think that you have loose wire or short possily a ground wire that could be not letting your system have full currrent. When was thwe last time the cap and rotor were changed and all that? Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted November 28, 2002 Share Posted November 28, 2002 My first guess is insufficient fuel flow. Low speeds (engine load) need less gas, higher speeds more. If the fuel delivery starts to lag, the float levels get low, engine goes lean and starts to stall, this uses less gas so, float level starts to catch up, .... you get the idea. Checking the fuel filters is the right place to start. Doing a general engine/fuel system inspection is also needed. Look for kinked lines, leaks, dirt, bad vacuum lines etc. Check the carbs, make sure the oil level in the SU's is good with the proper weight oil. Also make sure the (I forget what they are called) CV cylinders move smoothly. Check ignition as suggested above. Could be a vacuum advance issue, but my guess is fuel problem. A general check out is good practice anyway. If all good (and fix the tank leak for God's sake) then check the fuel pressure at the carbs, especially with a partially full tank. If you can mount the gage where you can see it while driving, then you should be able to tell if it goes low when the engine is stalling. But my guess is the fuel pump isn't getting it done. Do a flow check on the pump. My guess is one of the above will find the problem for you. Also the postings have been pretty slow lately. My guess with the holidays and cold weather, not many guys are working on their cars. Quote Link to comment Share on other sites More sharing options...
260ZRED Posted November 28, 2002 Author Share Posted November 28, 2002 I did my valves with my dad and now my top speed is about 65 MPH... a 15 mph improvement! The engine feels so much better now! Who ever's reading this... Don't forget to do your valves!!! Anyway, as soon as it gets to 65, the engine just starts going put put put very quitely and then the putputput just speeds up, but no power is made, and if the gas pedal is pressed, the engine does die.... Is it running to rich or to lean? I asked different people and got totally different answers. The wierd thing is my car ran just fine before and I have never even touched any carb settings! Can anyone tell me the easiet way to learn to adjust the SU's?? I will be gone for the next 4 days (holidays!) but I really appreciate anybody's input on this. I will change the fuel fitler and air filter first thing when I get back.....Could the dirty air filter be richening up my fuel mixture by any chance????? Is the stock air cleaner box (big orange unit) any good for performance? Thanks! Quote Link to comment Share on other sites More sharing options...
260ZRED Posted November 28, 2002 Author Share Posted November 28, 2002 forgot to say.... the ignition system is an electronic one of of a 280 with 'NGK?' wires and those wierd split sparkplugs....it was installed recently. Quote Link to comment Share on other sites More sharing options...
jc052685 Posted June 4, 2008 Share Posted June 4, 2008 i know this is a dead post but did you ever fix the problem? Quote Link to comment Share on other sites More sharing options...
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