# 86 Nissan 720, wont idle, very shaky



## tomcraw08 (May 22, 2012)

Hello I have a 1986 nissan 720 pickup, the engine has been replaced with a similar nissan z motor from the previous owner. The car has been running fine until recently, which it will not idle at all now. I can start the engine with help from the accelorator and it runs okay at high rpms, but will immediatly shake roughly and start to sputter when i release the gas eventually killing the engine. It seems a bit starved for gas or air i cant tell. I have replaced all plugs, wires, cap, rotor, fuel filter, and even a few random ported vaccum switches but nothing has solved the problem. All hoses seem to be connected properly but i can not trace the problem. Help please!


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## living4kicks (Feb 8, 2015)

*720 idle problem*

is your truck TBI, may check the TPS and or timing


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## smj999smj (Jan 1, 2006)

If it's a 720, it should be carbureted. There are a number of possibilities. Some things that are possible that I've seen with these engines include: dirt in the carburetor requiring a rebuild, bad fuel pump (make sure you can see the fuel in the window on the side of the carb), failed head gasket (they commonly blew between the cylinders), leaking intake gasket, or a bad ignition coil.


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## living4kicks (Feb 8, 2015)

I have a 720 and it is TBI, does anyone know how many volts the TPS should be putting out. I know that 5v comes from the truck to the sensor. Also, could it be a air flow meter?


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## smj999smj (Jan 1, 2006)

The TPS should run a range of approximately 0.4-0.5v on the low end up to approximately 4.5v on the high end (with a minimum of at least 3.5v on the high end). These engines were prone to leaks at the intake manifold gasket and throttle body base gasket; try spraying carb cleaner in these areas while running and see if the RPM surges or "spikes." If it does, that could be your problem. You might also want to check for stored codes in the ECM.


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