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1978 280z smooth idle, spits and spudders while driving


sicripp83

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hey everyone just bought my first Z.   needs work but its all original. 1978 280z   it was in storage for 7 years before I got it.  the fuel has been drained and fresh fuel added, new plugs and wires, cap and rotor.     the car will start very easy and idle great.    it you try to rev it, it will spit and spudder. also while driving of course.    any suggestions on where I could start would be great.   thanks Josh

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*Update*        the car will rev while in neutral,   when you drive, it almost acts like it missing on a cylinder.   also you can still smell bad gas in the exhaust.    is it possible that I still have bad gas in the lines?   maybe change the fuel filter again.     checked the plugs and they look great.      thanks guys

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You're actually pretty lucky that it's driveable.  Bad things happen when these cars sit.

 

There are two paths you could take - 1.  Drive the piss out of it and see if things change.  They do seem to like hard work.  2.  Work your way through the Engine fuel chapter of the FSM (http://www.nicoclub.com/FSM/280z/), and/or the Electronic Fuel Injection Guide (http://www.xenons130.com/reference.html). 

 

Also, for some reason, many of the old EFI systems tend to run lean.  The spitting and popping is typical.  You could put a potentiometer on the coolant temperature circuit and dial in some extra fuel.

 

The phone is going to be a problem for you though.  Good luck.

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  • 4 weeks later...

hey guys     

still working on the Z   did some reading and found out that a majority of the problems with this fuel injection system are mostly the AFM and coolent temp sensor.   so I changed the temp sensor.  no change   I went to the local junk yard and grabbed a AFM from a 81 280zx.   put it on and it runs a little better.    but its by no means fixed  my question is the zx AFM working against me, in solving my issue?? 

 

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My AFM has screws on both sides that let's me adjust it. Does yours have them? Mine was running way too lean, but runs better now. My AFM is aftermarket, so I'm not sure if yours has the same setup. Sounds like a A/F ratio problem to me, though.....ever have problems starting up? If it's running really lean, I would imagine cold-starts being an issue. 

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it starts fine and idles great.  i went through and checked all the circuits as explained in the efi bible.   everything checked out as it should.   the previous owned told me he has drained the gas and put in fresh gas.      after looking further the gas tank drain plug has never been removed.  im going to assume that he just added fresh gas to 7 year old bad gas.   so i drained the tank tonight, smelled bad!    tomarrow im going to drop the tank and give it a look and clean it out.

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  • 4 weeks later...

I am totally new too the z, just got one this week, however not new cars at all. This sounds like a distributer problem. Likely with something that holds the distributer, that's why it will idle and rev in neutral but not under load. Many cars have a barring that holds the distributer, when that gets loose or breakes it causes these exact symptoms.

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  • 2 weeks later...

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