nscason Posted December 22, 2006 Share Posted December 22, 2006 Ok I need some insight. I cracked the head of my 77 280z the summer before last. I was "given" a new head and added a lot of stuff while it was off. 3 into 2 header, no more smog crap, big bore tb, aftermarket fuel rail, zxt fuel pressure reg, zxt injectors, cranecams xr3000 ign and e core coil. thats just to name a few of the thing i have done. anyways the car runs great. its just the idle. let me be more specific. If i have the idle where it should be when the motor is wormed up(800-900rpm) it wont stay running when I start it up when it is cold. I have to give it a little bit of gas to keep it from stalling. On the other hand if i have the idle set up to where it runs at about 700rpm when it is cold once it worms up all the way it'll run at 12-13 hundred rpm. now that its winter time it has been a real pain in the butt. any outside thought would help. thanks nick cason Quote Link to comment Share on other sites More sharing options...
nscason Posted January 24, 2007 Author Share Posted January 24, 2007 i put this one up one month ago. are there no takers? no ideas??? my car has been like this for the longest time, but it hasnt really bothered me. it just gets annoying when the weather changes dramatically. thats about it though. Quote Link to comment Share on other sites More sharing options...
DCZ Posted January 24, 2007 Share Posted January 24, 2007 Are you running the stock ECU with turbo injectors? If so you are probably running way too rich and that could cause what you are seeing. The turbo injectors flow too much fuel if you are using the N/A ECU. Quote Link to comment Share on other sites More sharing options...
nscason Posted January 24, 2007 Author Share Posted January 24, 2007 yes. i do have the stock ecu and me car is n/a. will putting on an adjustable fpr help or is a lower psi not going to affect the overall flow? how can i tell if im running rich or lean without getting one of those auto meters? or do i want to get one? does a zxt ecu control the fuel flow better or something? i figured that with more air going in and out of the motor and a hotter spark i would be ok with the zxt injectors. i have only had my car for about a 1 1/2 years and dont quite know all the things to get a good performing motor yet. dont get me wrong it runs great, im still learning though. any help would be great. thanks Quote Link to comment Share on other sites More sharing options...
DCZ Posted January 25, 2007 Share Posted January 25, 2007 I'm not an expert but here's my "limited" viewpoint: >will putting on an adjustable fpr help or is a lower psi not going to affect the overall flow? Lowering the fuel pressure would probably help - less fuel would squirt through each time the injector opens - but you would be shooting in the dark trying to figure out the right pressure. Also the right pressure at one rpm would likely be the wrong pressure at another. >does a zxt ecu control the fuel flow better or something? The N/A ecu is programmed to inject "Y" amount of fuel based on "X" amount of air that is measured by the AFM (this is a simplification but that's basically how it works). It does this by varying the length of time that the injectors are open. The ZXT injectors will flow more fuel during that length of time and the N/A ecu can't compensate enough to work well. I would guess that the turbo ecu would make the problem worse b/c you don't have that turbo stuffing more air into the engine. >i figured that with more air going in and out of the motor and a hotter spark i would be ok with the zxt injectors. I don't think you are getting the amount of air into your engine that you would if you had a turbo. It's not so far off that the engine won't run, it just doesn't run as well as it would if the injectors were the right ones. If you had a standalone programmable ecu you could adjust things to work with the higher flow injectors but I don't think there is anything you can do with the stock ecu. Don't take everything I say as the final word, as I said I'm no expert! Quote Link to comment Share on other sites More sharing options...
twoeightythreez Posted January 25, 2007 Share Posted January 25, 2007 You can run the ZXT injectors, you just have to tweak the idle and midrange mixture. Search the site, several people have detailed how to "tweak" the stock EFI. You basically adjust the clockspring inside the AFM to get a good idle and adjust the temp sensor resistance (with a potentiometer) to get good midrange. Quote Link to comment Share on other sites More sharing options...
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