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 Post subject: 280zx Hesitation Issue
PostPosted: Tue Jan 29, 2019 10:06 am 
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Joined: Thu Oct 08, 2009 1:14 pm
Posts: 206
Location: Southington, CT
Hi all - I was recently fortunate enough to get my hands on a 1980 280zx with 66k original miles. Beautiful shape, but it had sat for many years and needed some love to get it up and running again; specifically: fuel drained, new fuel filter, cap, rotor, wires, plugs. It starts and idles just fine, but when I hit the throttle as I would normally from a stop, it initially bogs down, sputters and pops pretty significantly before regaining its footing and revving normally in the higher rpm range. I realize that this could be from a host of things, but has anyone ever dealt with this type of issue before? ..perhaps in reviving a Z from years of slumber like this?

Any input would be greatly appreciated!


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PostPosted: Tue Jan 29, 2019 11:51 am 
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Joined: Wed Apr 09, 2008 5:53 pm
Posts: 13041
Location: CT
My money is on either a vacuum leak, fuel or ignition issues.
Does engine temperature matter? Is it a turbo?

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PostPosted: Tue Jan 29, 2019 12:52 pm 
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Joined: Thu Oct 08, 2009 1:14 pm
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Location: Southington, CT
Non-turbo. And no, it seems to behave this way no matter how long it's been running (cold or idling for a long time).


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PostPosted: Tue Jan 29, 2019 6:57 pm 
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Joined: Wed Apr 09, 2008 5:53 pm
Posts: 13041
Location: CT
This will sound weird, and it might not have anything to do with your problems, but please pull the air cleaner open and check the filter. It's on the 'cold' side of the radiator.
I helped a new zx owner start his neglected 280 once and found such a huge mouse nest in the air intake, the engine could hardly breathe, and a small mouse actually got sucked into the valveworks.
That might not have anything to do with you, but it should be on your preflight checklist, anyway.
I'm almost ignorant about the fuel injection systems, so I have nothing of value to offer there. But your electronic ignition advance should be checked for full function. Vinny's an expert on this stuff. 860-355-182nine.

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PostPosted: Wed Jan 30, 2019 10:11 am 
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Joined: Thu Oct 08, 2009 1:14 pm
Posts: 206
Location: Southington, CT
Thanks for the advice, Frank :thumbs_up: I did indeed check the air filter, and it looks brand new with no evidence of critters. I'm no mechanic, but I do have the factory service manual and I'll go down the checklist of possible culprits to the best of my ability. If I get nowhere I'll be sending it off to a reputable garage in town.


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PostPosted: Wed Jan 30, 2019 12:12 pm 
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Joined: Wed Apr 09, 2008 5:53 pm
Posts: 13041
Location: CT
It's called a 'transition stumble' if you need to describe it over the phone. The engine works well at idle and at high speed, but trips over itself trying to change its mind.

Both fuel delivery and ignition 'change their job' during that transition. Either of them is designed to run at low (idle), medium (traffic) and high speeds and they have specific mechanisms to meet each of those demands. Something is preventing one of those systems from transitioning smoothly.

To check for a vacuum leak, start the COLD engine and let it idle while you spray a can of starting fluid all around the engine. If you have a vacuum leak it will suck the hi-test fluid into the engine and the revs will momentarily increase when you spray that area. That at least gives you a place to start digging.

Please don't do that with a hot engine. :roll:

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