bumble zee Posted September 11, 2002 Share Posted September 11, 2002 76 280z with a 81zxt engine, stock turbo, 10 #'s of boost have a 76z intake manifold, volvo intercooler, 2.5" straight exsaust. When i get i the high rpms..like around 5000, i lean out, to the point of where the a/f guage doesnt read anymore. now i changed out the ecu a couple of days ago, and i ran perfct again... but now its like it learned to lean out again... what would cause this problem?? Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted September 23, 2002 Share Posted September 23, 2002 Just a stab in the dark, but have you tried replacing the fuel filter? Quote Link to comment Share on other sites More sharing options...
bumble zee Posted September 23, 2002 Author Share Posted September 23, 2002 yes i have Quote Link to comment Share on other sites More sharing options...
jeffp Posted September 23, 2002 Share Posted September 23, 2002 ok, here is what you should do. First let me rant a little. Not saying you do this, but I will never understand why people have problems with their fuel management and dont take the time to effectivly trouble shoot the entire system to determine exactly what is wrong. ok, now I am done with that. From your O2 readings you have a couple problems that could cause the lean condition. The first thing you should do is get a fuel pressure gauge on the car and make damn sure the fuel pump can and does provide the required amount of fuel for the engine. The fuel gauge should never decrease in pressure, unless you let off the throttle, so when you come up on boost the pressure should increase 1 psi per 1 psi of boost, you should NEVER see a wavering gauge needle when you are increasing boost. Really the very best way to check the system is this. figure out what your max boost will be, then get a regulated air supply and push the fuel pressure up to 36.6 + the boost boost psi(36.6 + 15 psi boost= 51.6 or 52 psi at the fuel gauge.) then calculate how much power you want from the engine and convert that to fuel requirements in cc's (example 60hp per cylinder requires say 400cc's per minute) then you add all of the injector flow rates together 2400cc's per minute. then you pressure up the regulator with your boost from the regulated air source(a mig welder 02 bottle and regulator works excellent) turn the pump on and put the return line into a gallon jug. Time it for a minute and see how much fuel is in the jug, if you are less then what you calculated for cc's per minute, then you need a better pump. You can do all of this without ever cranking the engine, and that is where allot of guys go wrong, they setup their cars to do 350-450hp and they dont have a delivery system that will provide enough fuel from the start and wonder why they have problems. You just have to check the whole system, and then decide where you need improvements. hope that helps Quote Link to comment Share on other sites More sharing options...
bumble zee Posted September 23, 2002 Author Share Posted September 23, 2002 hey jeffp... i di have a fuel pressure guage in the line where i can see it at all times... idle its at 30lbs and in full boost, 50lbs at 10#'s of boost... i have went through the afm reading voltage ohm's.. checks out... have been talking to scottyMIZ alot and he and others have come down to the head temp sensor... so im replacing that.. in fact scottyMIZ was here this weekend and i cleaned my injectors and then put it back together.. ran the same.. but as i started it more and more and drove it it seemed to be running fine now... still replacing the head temp sensor. ScottyMIZ raced a 12 second elipse.. if he got just a bit of a better launch.. my god, he woulda beat him... but he was right on him... Quote Link to comment Share on other sites More sharing options...
scottyMIz Posted September 23, 2002 Share Posted September 23, 2002 so it's running good now ferg?You got a good race too with dave it was close(you need to turn up the boost)I wish that id would have given me another chance to run i think it would havebeen a different story and i would have warmed up the tires first too.Oh well i'l get him next year Quote Link to comment Share on other sites More sharing options...
J Taylor Posted October 1, 2002 Share Posted October 1, 2002 Unplug and spray your ECU connections with wd40 and see if that helps. These cars are really bad about having bad connections there and making the cars lean out. Alot of times all you have to do is unplug it and plug it back in and the problem is solved. JT Quote Link to comment Share on other sites More sharing options...
bumble zee Posted October 1, 2002 Author Share Posted October 1, 2002 it is fixed.. cleaned the injectors, and got a head temp sensor... its all good now Quote Link to comment Share on other sites More sharing options...
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