280zx Fever Posted January 18, 2004 Share #1 Posted January 18, 2004 Ok im stuffed if i know.... Car has been idelnig high for a while.. car in question is 1979 280zx Fairlady Z N42 Top and bottom.. So i decdided to swap afm with my other 280zx.. 1981 280zx P90 Head and F54 Block... When i did this the car ran fine... ideled nicely at 1krpm before it was 1.5/1.6k.. BUT now it back fires through the afm when i rev it up and its not as responsive.. Could the throttle position sensor be differnt ?? so the afm isnt opening enough causing it too over fuel ? Anyone experiance this problem ? I havent tried the old AFM in the other car... thats what ill do now Thanks Link to comment https://www.classiczcars.com/topic/9776-l28-air-flow-meter-trouble/ Share on other sites More sharing options...
Gav240z Posted January 18, 2004 Share #2 Posted January 18, 2004 hmmm usually backfire through the intake is a result of a lean condition.I am not an EFI expert so this is kinda a hard one for me.Is it possible that both AFM's are faulty?How did the other car run?By changing the AFM you could have changed a few things that were set up with the tune of your old AFM.Could even be electrical timing. although I'm not saying it is.Good luck.Gav, Link to comment https://www.classiczcars.com/topic/9776-l28-air-flow-meter-trouble/#findComment-64788 Share on other sites More sharing options...
280zx Fever Posted January 18, 2004 Author Share #3 Posted January 18, 2004 To my best knowlege all parts are virutually interchangable between all L28 engines... The P90 Intake has only 1 butterfly whislt the N42 Intake has 2 1 larger and 1 smaller butterfly... So the throttle postion sensors may be differnt.. Like its not registering the second butterfly.. ? I never got to start the second car.. yet.... damn flat batterys plus it needs some fuel ill get her running today hopefully and get back to you all Link to comment https://www.classiczcars.com/topic/9776-l28-air-flow-meter-trouble/#findComment-64816 Share on other sites More sharing options...
Zvoiture Posted January 19, 2004 Share #4 Posted January 19, 2004 Coupla things to check VERY CAREFULLY...The intake hose from the AFM to the TB. There could be a crack or air leak that was modulated by the change in AFMs. Perhaps it didn't leak quite so bad with the new one? Cracks are usually right around the seats anyway. If you got the new one in a bit further....not so much leakage.Vacuum leaks. Check (or better yet REPLACE) every single vacuum hose. Make sure you get the right size and that all ends are tight. Is there an O-ring in the dixxy? Is your dipstick tight? FI motors don't like vacuum leaks.When you adjust the TB by hand to adjust idle speed, does it respond?steve Link to comment https://www.classiczcars.com/topic/9776-l28-air-flow-meter-trouble/#findComment-64830 Share on other sites More sharing options...
280zx Fever Posted January 19, 2004 Author Share #5 Posted January 19, 2004 No vaccumn leaks around at all..Now, there are two screws that look like they adjust something coverd by rubber plugs.. what do they adjust ?Also the car has no pick up or down when screwing in the idle screws on the throttle body. Link to comment https://www.classiczcars.com/topic/9776-l28-air-flow-meter-trouble/#findComment-64890 Share on other sites More sharing options...
Yarb
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