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Discussion Starter · #1 ·
I mentioned I'm also having this issue in a post about my clutch. I was asked to give details about my lack of power and here's what I said:
"The running problem I'm having is tuff to explain... At first it wouldn't rev past 3,500 RPM. Then as it gets warmer under the hood(not coolant temp. That stays good) it'll lose power at a lower & lower RPM. At first I can cruise as high as 55, then it's hard to even hit 20.
In trouble shooting this; I replaced the vacuume line that plugs in right in front of the throttle body. Now in neutral I can rev it up all the way, but in gear (under load) I have the same problem.... Any thoughts?"
That's my issue. I can put around town slowly, but can't hit the highways. Anybody know what has gone bad? Should I replace all my lines or something? It's a 280ZX by the way

Thanks
 

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1983 280zx n/a 5-speed t-tops
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Just a couple things to get the discussion going: have you/can you check timing - ensure timing advances properly with RPM. Check vacuum and vacuum response with RPM. Check operation/condition of the cylinder head temp sensor. Is the car equiped with california of federal emissions? Each has several vacuum operated devices. Theres also an altitude switch that affects the ECU but I dont think you should be affected by that.

Or, could be in the fuel system. Check fuel pressure under different RPM. Fuel restrictions, blockages in the fuel or evap/vent lines. Check fuel pressure regulator operation under vacuum.

Thats not all but should give more clues.

Can't remember your experience with the S130 so let us know what you find or need help finding.
 

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1981 280zx GL na 5spd
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If your problem is fuel related I would recommend checking out the fuel sending unit in the tank. My 280zx was sitting for a few years before I bought it and the sending unit tubes were completely blocked with a thick black gunk (probably dirt mixed with the varnish fuel). I'm assuming this is something that just happens to these cars after sitting, worth checking on it if your Z has been parked for a looong time
 

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Discussion Starter · #4 ·
My Z has not been sitting for a long time. In fact it used to run great. This problem just trickled in... My buddy Guy (Z Doctor) said he suspected it to be either a seal break or a clogged exhaust.
To test this I sprayed Starting fluid all over the air intake system while idling and disconnected my exhaust under the manifold. There were no changes in idle and no driving changes so intake or exhaust don't appear to be the issue... The fact that in neutral it revs ok, but not in gear; makes me think maybe it's a vacuume thing.
Please keep your thoughts coming. I miss my Z 😢
 

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Discussion Starter · #5 ·
Since this first started I've been feeling the issue is somehow vacuume related... Unless you guys have other thoughts, I think I want to replace all the vacuume hoses, plugs, components. Anybody know where I can find a whole vacuume kit to replace anything vacuume related?
 

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Pull your plugs and see what color they are. Black is rich, white is lean. Either you don't have enough air (rich black plug) or you dont have enough fuel (Lean too much air = vac leak white plugs).
 

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Discussion Starter · #7 ·
Pull your plugs and see what color they are. Black is rich, white is lean. Either you don't have enough air (rich black plug) or you dont have enough fuel (Lean too much air = vac leak white plugs).
I wouldn't have guessed it was a sparkplug issue. You're thinking it is? The plug doesn't look like I'm running to Rich or Lean. It's a brown color. Should I replace the plugs for this issue anyway?
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Checking the color of the plugs is a good way to check what your engine is doing with the fuel. Google spark plug color chart to see what I mean. You don't seem to be running rich. If the plugs are grey or brown that is normal.

This could be a CHTS that is giving a high ohm reading when warm, or a distributor advance issue, or a throttle position switch issue or a AFM issue or just a bad electrical connection issue. Do the diagnostic checks, it will help eliminate all of the above. DON'T mess with the AFM unless you can prove without a shadow of a doubt that there is an issue with it. The AFM checks are in the diagnostic procedure.
So you should download the FSM and go thru the diagnostic procedure and test everything fuel and ECU related. It is the only way to really check things out. Get the FSM free here.
XenonZcar.com S130 Factory Service manuals
Since you didn't give a year of your 280zx I cant point you to a starting page.
 

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Discussion Starter · #11 ·
Checking the color of the plugs is a good way to check what your engine is doing with the fuel. Google spark plug color chart to see what I mean. You don't seem to be running rich. If the plugs are grey or brown that is normal.

This could be a CHTS that is giving a high ohm reading when warm, or a distributor advance issue, or a throttle position switch issue or a AFM issue or just a bad electrical connection issue. Do the diagnostic checks, it will help eliminate all of the above. DON'T mess with the AFM unless you can prove without a shadow of a doubt that there is an issue with it. The AFM checks are in the diagnostic procedure.
So you should download the FSM and go thru the diagnostic procedure and test everything fuel and ECU related. It is the only way to really check things out. Get the FSM free here.
XenonZcar.com S130 Factory Service manuals
Since you didn't give a year of your 280zx I cant point you to a starting page.
Thanks for this insight... My 280ZX is the 1980 A.E.
 

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Discussion Starter · #15 ·
Any idea to what's causing my issue? Maybe I should plug all my unnecessary vacuume lines and see if anything changes. 🤔
 

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post #9
Checking the color of the plugs is a good way to check what your engine is doing with the fuel. Google spark plug color chart to see what I mean. You don't seem to be running rich. If the plugs are grey or brown that is normal.

This could be a CHTS that is giving a high ohm reading when warm, or a distributor advance issue, or a throttle position switch issue or a AFM issue or just a bad electrical connection issue. Do the diagnostic checks, it will help eliminate all of the above. DON'T mess with the AFM unless you can prove without a shadow of a doubt that there is an issue with it. The AFM checks are in the diagnostic procedure.
So you should download the FSM and go thru the diagnostic procedure and test everything fuel and ECU related. It is the only way to really check things out. Get the FSM free here.
XenonZcar.com S130 Factory Service manuals
Since you didn't give a year of your 280zx I cant point you to a starting page.


How much of the diagnostic procedure have yo gone thru? Any?
 
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