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Barely starts and won't idle. L28et tune diag.

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To start with, here's a rundown on the setup:


'78 280z

-L28ET, 0.5mm overbore, ITM pistons, full internal balance

-Late 'A' grind cam from a late Z/early ZX

-Rebuilt head: Minor port cleanup and 5 angle valve cut

-'76 non-emmissions intake, stock turbo TB with 240SX TPS

-Custom equal length header with Nissan 45v1 turbo (R33 GTS-25t), 8 psi wastegate actuator 

-Denso 440cc fuel injectors (Mk3 Supra) with stock Z resistor pack

Aeromotive fuel pressure regulator set to 26 psi @idle, rises to 30 psi when throttled

-Ford EDIS 6 ignition system: Explorer controller, '06 Mustang coil pack, Escort 1.9 CKP sensor, custom 36-1 trigger wheel and sensor bracket


Running MS2 V3.0, firmware 3.4.1, ZXT chts, GM iat sensor, no idle air control, although I eventually plan to use the factory fast idle valve. 


Also using an Innovate SCG-1 wideband/boost controller. 


My problems are: it will barely start, especially when the engine is warm, and will not idle on its own, requiring constant blipping of the throttle. When attempting to rev the engine or even keep it running, it backfires out the tailpipe, which tells me it's running rich, and yet it will occasionally pop through the intake, which tells me "lean". The wideband's display is all over the place, reading pig rich when starting and running for the first bit, then it starts jumping randomly between 12:1 and around 16:1. Then if you either leave it to idle or press the gas, it just gives up and leans dead... 


The chts and tps are already calibrated, I've gone through various tunes, even changing cells, only for it to kind of work better, but have another aspect of it worse (eg. Better idle but worse intake popping). Currently trying one of Cygnus' older map sets since their engine setup is similar to mine. 


Here's some pics of what I have so far. I'm looking for some insight on this. Another important thing to note, is that I live in Alberta, Canada, which is roughly 3500 ft above sea level, which might skew timing and fuel a bunch. 


I appreciate any help. 









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What do the plugs look like? Have you started with a fresh set? IMO, when you are trying to set a base tune, you will be going through ALOT of plugs.


Post a pic of the condition of the plugs, buy a few sets of new plugs, make sure you 100% accurate with your trigger wheel offset calibration and we can start from there.



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Post a log of cranking and idle.  Also, I do not see it in your post but did you set the timing under fixed prior to using the table?  Also your VE table values do not look like they may be helping since near idle vac the difference in values are around 10 which will cause the wideband to jump.  Post a log so we can see your idle and be able to help more accurately.

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