Where to Start?

[Nismorunner182]

Hello friends,

I know this is probably something that has been answered to some degree but I need some help.
A little back ground, I love nissan I've owned three now, and just the other day I bought my first 1991 NA 300zx. Been wanting one since I was a wee lad.

Anyway, here's my issue,

The car starts all the time, every time. It seems to idle at 950 upon start up, then drops down to 500 and sputters and sometimes dies unless I give it gas. However, when I do give it gas, it raises to 1500 and then starts to dip down again (even with me still holding in the gas pedal) unless I feather the clutch and the gas and sometimes it still dies. It wont accelerate past 10mph.

The MAF was recently changed looks brand new.

No Vaccuum leaks as far as I can tell, but haven't formally tested.

I'm assuming the spark plugs are fine because it fires well, however I understand there is a specific type of plug that is universally recommended. I don't know how legitimate that is but, I'm open to possibilities.

The TPS looks just fine, almost new.

The Idle screw may need adjusting but I don't know if that would solve the issue regarding acceleration?

I am going to replace the coolant sensor, because it was corroded, and I know that if the connection is bad, the ECU will make the fuel system too rich in order to falsely cool the combustion chambers. And upon start up on an already cool motor, that sucks. (Still doubt that's the problem but you never know)

I had one friend tell me it could be clogged cats from running too rich.

The fuel filter is brand new,

If i'm not mistaken I think I hear the fuel pump too, Not sure if if being that loud is normal, even if that's what that is.



Sorry for the long newb post, but I appreciate those of you that can help me. I'm hoping it's a simple fix just so it's at least drive-able. I just need to know where to start.


Thanks guys.

[centralcoaster33]

Hey, welcome to the Forums! MAF and TPS are a good place to start looking. Idle valves also. If this car is like my 240sx, you don't mess with the "idle screw" on the throttle body. You turn the idle screw on the idle air control valve. So, until you're sure, don't tinker with that screw. You should download your FSM. You should check your ECU for codes at that point. That will help point you in the right direction. Next I would use the instruction in there to test the bits with a voltmeter, MAF, TPS, IACV and timing. Good luck and let us know what you find!

http://www.nicoclub.com/archives/nissan ... nuals.html

[Nismorunner182]

Thank you Sir!

I guess I'll just test what sensors are bad with the voltmeter and replace them accordingly. After that I'll look into the fuel system.

Thanks again man, I went ahead and down loaded the manual provided. I'll let you know how it turns out!

[DCaff300ZX]

Welcome!
You will want to check for any codes at the ECU, a very important start. If no codes found (55 reading) then further tests are in order, the fsm has a very good and thorough testing procedure to get started.
At this point it's hard to pinpoint anything, but the coolant temp sensor is a good thing to fix for the reason you gave, plus it will cause other issues...be sure BOTH connectors are good and replacing the CTS itself is never a bad idea, and not expensive at Z1 or Concept Z. The CAS connector and IACV, fuel injectors (you have the old style, prone to failure), and PTU harness can also be part or all of the issue, but tests should help pinpoint a specific issue. Be aware though that if you find green corrosion in the connectors, that is a huge part of your issue and they need to be cleaned or replaced with upgraded weatherproof connectors.
Good Luck!