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Trying to get my '75 280Z running right.. could use some help

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I just finished refreshing my intake manifold/injectors/ignition system and I'm attempting to get this thing running right.  Having never before actually experienced a properly running Z, I feel like I'm going in circles trying to get it to where it is somewhat healthy.  Here is where it sits as of this evening:

It'll start after a few cranks, but usually dies a few times, then picks up a high idle (maybe 1500ish).

The idle will come down to about 1200 RPM after it warms up (about 2/3 to 1/2 on the temp gauge).

The conditions at that point (its fairly steady here):
RPM: 1100-1200
Timing: ~15 BTDC on the crank pulley (this is where it seems to be happiest)
Vacuum: Just over 20 inHG (needles vibrates a bit)
AFM Idle screw: 3.5 turns from fully in (I don't adjust this; I just ran it in and backed it out to the same spot to see where it was)
TB Idle screw: 4 turns from fully in
Fuel pressure: pretty steady at 28psi
Revs readily, no hesitation and sounds pretty smooth at high RPM
Have not driven it in this condition to assess its performance under load; don't want to get stranded

The exhaust smells pretty funky, like it is running super rich.  It'll also 'chuff.. chuff chuff' here and there.  It seems really sensitive to the TB idle adjust; if I turn it in or out even half a turn it'll die.  Same with the timing; a few degrees in either direction (especially decreasing) will kill it.  I can't seem to get it to idle at any lower RPM without it dying though. 

From what I understand, I'm shooting for a lower idle (800-900), but I just can't seem to adjust it to there without having it die.  And the funky exhaust has me worried the neighbors are going to complain at some point. 

Some more relevant information on the engine: its a maxima N47 head on a 280ZX block (courtesy of the PO; not sure why or how this came to be).  I know this produces higher compression, but I'm hoping its still close enough to stock to where it will work with the stock FI system.  Pistons look dished, camshaft I'm assuming is the one that came with the maxima head (Its internally oiled, doesn't look new).  The EFI bible checks for the AFM are passing EXCEPT the pins 7-8 resistance check (which says 'continuity, very small resistance' or something similar but is reading as 145ohms).  New NGK plugs, coil, wires, freshly refurbed distributor; lots of recently added blood/sweat/tears. 

My next step is going to be getting the AFM rebuilt.  From there.. not sure. 

Anyway, sorry for the long post.  Any help/opinions would be more than welcome 🙂

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Are the injectors the stock "green top" injectors?  And have you measured the resistance of the coolant temperature sensor?  That test is in the EFI Book.  Could be that the PO installed "turbo" injectors.  Never know.  Or adjusted the AFM.   Or that your coolant temp. circuit is open.

Try moving the AFM vane by hand and see if it runs better.  You can move the weight under the black cover.  Close it and the ECU will supply less fuel.  Might tell you if the AFM could use adjustment.  Your fuel pressure looks pretty good for what you're experiencing.

Here's your other thread - 

 

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Injectors are all fresh refurbs from RockAuto; I ordered all 6 at once.  4 came in 'green top', and 2 are kind of a beige color.  I figured they were equivalent.. might be a bad assumption though.  Picture attached

The coolant temp sensor is new, and seemed a little high on the resistance (just checked it again, 1050 ohms @ 110F) but its pretty close to the values in the manual when interpolated.  Maybe 5% on the high side.  I'll recheck it again when the engine is completely cool.  I checked it back when I installed it.. should have written down the values but I came to the same conclusion then.  

And PO was definitely in the AFM; it had 2 different types of glue holding the black cover on.  I'll try pushing the black weight around a bit tomorrow night and see what happens.  Nervous about messing with that thing..

I can move this over to my other thread if you think that'd be more appropriate; didn't mean to go starting a new thread unnecessarily.  On the plus side I did figure out the timing issue (with tons of much appreciated help from yourself and others!), so I figured I'd start a new one. 

Regardless, thanks for the response 🙂 

IMG_20181120_193851.jpg

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What did you do with the cold start valve?  Is it hooked up and fueling, could be a cause for the overly rich smell.  Try unhooking it and see if things change, plug or clamp the fuel hose too.  Good luck.  You have a good helper already. 😊

Have you checked to see if the TPS is on the idle side?  People bend those vanes and screw them up, it might have been rotated too.  

http://www.atlanticz.ca/zclub/techtips/tps/index.html

tpsidle.jpg

Edited by siteunseen
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4 hours ago, siteunseen said:

What did you do with the cold start valve?  Is it hooked up and fueling, could be a cause for the overly rich smell.  Try unhooking it and see if things change, plug or clamp the fuel hose too.  Good luck.  You have a good helper already. 😊

Have you checked to see if the TPS is on the idle side?  People bend those vanes and screw them up, it might have been rotated too.  

http://www.atlanticz.ca/zclub/techtips/tps/index.html

 

I did try unplugging the cold start; no change.  But good point clamping the hose.  I'll give that a shot tonight. 

And I'll definitely revisit that TPS; pretty sure I set it where it needed to be when I was reassembling my TB/manifold.  But, come to think of it, that may have been before I found that my throttle valve wasn't fully closing due to the little stop screw on the engine side being slightly too far down (found that when the TB Idle screw wasn't killing idle even when all the way screwed in).  Definitely rechecking that now..

Thanks!  Yeah.. I feel like I owe half of y'all a few beers already from my previous cries for help..  Zed Head for sure 😄  

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