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Ok guys, Im new to the site here, but a long time lover of all things Z. I have a 1990 300ZX Twin Turbo, and this morning she presented a problem to me that I have not yet been able to understand or research.

The car usually fires right up as soon as you turn the key, but this morning when I sat down in it, she turned over and died out. Turned over again and failed. On the 3rd start I got her running, but had to give it a bit of throttle to keep it running from the get go.

Now I said it started, but it was running very poorly. The RPM's usually sit between 5 and 7, but now it fluxes between 5 and 12. While the fluxing the car will occasionally have the slightest "bump" and the exhaust sound has a quick break in the note. Under any acceleration in first gear she has random hesitation in the throttle.

Under the hood, the sounds are a little more pronounced. I can hear the hum of the engine and the momentary break in the tone which sounds to me like a missfire, but I am not a mechanic. While all this is going on, there is a ticking coming from the top of the engine somewhere, which sounds much to me like and electrical contact firing improperly. This light ticking noise sometimes has a pattern to it, and sometimes it does not.

When this problem persists, the engine smells almost like it is running rich.

What I have done:
I have checked all the wires on top of the engine to be sure everything is connected, but nothing seems to be amiss. I did not check the TPS. I did not check anything below the manifold area of the engine. I ran the ECU in diagnostic mode, and flashed me a 55 so nothing on the ECU list is going wrong, then ran the ECU Mode II check on the O2 sensors, both right and left, and when I hold the throttle at 2000 RPMs, the check engine light flashes like I suppose it is meant to, though the flashing is by no means uniform. I have not yet called nissan to see if the PTU was ever replaced in this car.


As before stated, I am not a mechanic but I love these cars and I love to learn, so if you have any insight, I would appreciate any of your wisdom.


Thanks a ton.
 

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My car is doing something similar, it back fires and hesitates from no where. Mine is more then likely a clogged catalytic converter or something with a rotar. You might have a slight clog in your converter. Could also just be a dirty EGR. Clean your EGR and see if it runs fine.
 
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