Blackbob Posted May 21, 2006 Share Posted May 21, 2006 Can someone please explain to me why you can have one mass air let you just idle and another not idle but let you go to redline ? Same car as last time (87 300zx turbo) with the funky compression and so forth. Has killer oil leaks, oil pan gasket is non-existent and turbo return was a slacked job. Put the intake mani back to near stock jost about everything is hooked up except IACV and PCV valve. I'm going to hook those back up and see how much further I get in the mean time I'll try not to burn this damn car to the ground. The good news is it starts by the key and fuel pump works consistently . Quote Link to comment Share on other sites More sharing options...
Guest toadnz Posted May 22, 2006 Share Posted May 22, 2006 fuel mix info : http://ffp-motorsport.com/tuning/engtun.php?id=1'>http://ffp-motorsport.com/tuning/engtun.php?id=1 http://ffp-motorsport.com/tuning/engtun.php Nissan ZX's 89+ I've read about... if the ecu gets no MAF feedback voltage max revs are about 2600 rpm - unplug it and see... I did... say, if its a high voltage level, it will think the engine is sucking in heaps of air, and over rich the engine - especially at idle, till it stalls... mine did Once a good one was installed, its sweet. Yep Even when a bad one was plugged in - easiest to drive at > 3500 rpm - 'cause its not used... slightly over the speedlimit > 3500 rpm in top... never mind... MAF Good till about 3500 rpm, good for fuel economy lower engine speeds after 3500 rpm the ecu goes closed loop and uses 02 sensor and ROM maps in the ecu to work out injector pulse width, or something like that anyways so its not important its working at higher revs check out http://zhome.com/ZCMnL/PICS/hesitation/hesitation.html for more info on ecu's also twinturbo.net etc... Quote Link to comment Share on other sites More sharing options...
Blackbob Posted May 23, 2006 Author Share Posted May 23, 2006 But what would explain the two different feed backs from two different MAFS ? Quote Link to comment Share on other sites More sharing options...
Guest toadnz Posted May 23, 2006 Share Posted May 23, 2006 one MAF is working correctly, letting the engine idle and run well upto 3500 rpm the other maf is stuffed, no good, so car wont idle and revs like a crap upto 3000 odd rpm , However - over 3500 rpm the MAF is not used, so the engine will rev quite happily, with either a good or stuffed MAF. EXCEPT : if you unplug the MAF or the MAF is DEAD or sends an out of bounds voltage - say 12 volts instead of the 0.3 - 3 v then the ECU says sod this and max revs are 2500 does that help ? Quote Link to comment Share on other sites More sharing options...
Guest toadnz Posted May 23, 2006 Share Posted May 23, 2006 The fault can be a transistor,resistor,cap, or an open circuit to the heater wire, or hot return wire, shops do repair them, but I dont know how. Are you asking how do they really work ,rather than how can you can rev over 3500 even if its stuffed ? Quote Link to comment Share on other sites More sharing options...
Blackbob Posted May 23, 2006 Author Share Posted May 23, 2006 No no I got it now. Quote Link to comment Share on other sites More sharing options...
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