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1984 300zx engine stumbles and will not rev

440 Views 3 Replies 3 Participants Last post by  HenryD
Have a 1984 300zx Non-Tubo.The only way Ican get it to run is if I block off the return line,then it will run fine
but the idle is erratic. So far I have changed the fuel pump, fuel filter, fuel pressure regulator, fuel injectors and connectors, Mass Air flow sensor. If you unblock the return line the car stumbles and will not rev up and you cannot drive it. The fuel pressure is in spec. Running out of ideas. Please Help Me!
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Do you have a copy of the FSM for the 84 Z31?
How was the engine running before you changed all those parts? (did it start having the issues after or before)
were the parts you changed actually bad?
did you adjust the idle control valve in any way?
have you checked for vacuum leaks? there are many vacuum sources on the VG30

fuel pumps are not known to go out on these cars

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