# 300zx 1990 NA Erratic Idle ....hesitation. !!!



## Diny (Apr 25, 2005)

Hello All

I just got my 1990 Nissan 300zx NA (2-seat, with AT) from the mechanic and.... after performing a full plenum cleaning, replacing plenum gasket, replacing the sparks with double plat new ones, replacing the injectors cables, vaccum hoses... replaced all water hoses, made a full timing belt maintenance (water hoses, water pump, belt, pullies...thermostat, other drive belts, new tension thing), replacing the two pcv valves... cleaning most of the electric conectors, replacing the two big radiator hoses, cleaning throttle bodies.... the car just still hesitate when going below 20 mph.... erratic and rough idles... and when cruising you can feel a "up and down" on the throttle response even when pressing steady to the throttle.

What could it be?????????? suggestions??? experieces??

Please advise
Thanks!!!!!!


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## Spongerider (Nov 18, 2002)

Diny said:


> Hello All
> 
> I just got my 1990 Nissan 300zx NA (2-seat, with AT) from the mechanic and.... after performing a full plenum cleaning, replacing plenum gasket, replacing the sparks with double plat new ones, replacing the injectors cables, vaccum hoses... replaced all water hoses, made a full timing belt maintenance (water hoses, water pump, belt, pullies...thermostat, other drive belts, new tension thing), replacing the two pcv valves... cleaning most of the electric conectors, replacing the two big radiator hoses, cleaning throttle bodies.... the car just still hesitate when going below 20 mph.... erratic and rough idles... and when cruising you can feel a "up and down" on the throttle response even when pressing steady to the throttle.
> 
> ...


Do a ECU Diagnostic,

Follow the link it is easy to do.

http://www.ttzd.com/tech/diagnostic/diagnostic.html


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## nambino (Nov 5, 2004)

Diny said:


> Hello All
> 
> I just got my 1990 Nissan 300zx NA (2-seat, with AT) from the mechanic and.... after performing a full plenum cleaning, replacing plenum gasket, replacing the sparks with double plat new ones, replacing the injectors cables, vaccum hoses... replaced all water hoses, made a full timing belt maintenance (water hoses, water pump, belt, pullies...thermostat, other drive belts, new tension thing), replacing the two pcv valves... cleaning most of the electric conectors, replacing the two big radiator hoses, cleaning throttle bodies.... the car just still hesitate when going below 20 mph.... erratic and rough idles... and when cruising you can feel a "up and down" on the throttle response even when pressing steady to the throttle.
> 
> ...


I had the same thing with my 1986 Nissan 300ZX Turbo. Ended up ordering the Air Regulator direct from Nissan, about $170Cdn and it runs great now!... Just be careful reinstalling it... Plus it's a new upgraded Air Regulator, instead of a round regulator (probably spring loaded), its a square (probably electronic.

Hope this helps.


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## Zen31ZR (Mar 24, 2004)

I was gonna say, unmetered air and a lean condition will cause rough idle and erratic cruise conditions.


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## mgh (Apr 1, 2004)

Diny said:


> replaced the sparks with double plat new ones


Are you refering to Bosch type plugs.....if this is the case get rid of and install NGK's....they do the best in our cars. I know that this alone will not solve your overall problem but it's a start.

I'm assuming you did all of this work to solve your idle problem.

My Z started out with this problem and it turned out to be a bad injector. Have you run and codes on your ECU ? The list of what to check could go on........Check out this site, it has some good information about erratic idle click on the TECH section.

Good Luck


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