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Nissan 300ZX not running properly

1990 Nissan 300ZX non-turbo Auto.


Purchased car not running with seized engine. Put used engine in car. Compression test good. Teeth on the T-belt have been counted several times to insure correct setting. I have extra ECU, PTU, CAS and coils. I have replaced all and it runs exactly the same.

So I start the car and runs smooth but very under powered. Like its not running on all cylinders. I can remove all three electrical plugs from the coils on the pass side and it does not change the way it runs. If I remove any of the drive?s side one?s it will die. I pulled the spark plugs and the pass side one?s are all wet with fuel. Using pass side coils and plugs I tested them by plugging them in and grounded them on the intake manifold. I pulled the CAS leaving it plugged in and turn it with the key on and all coils and plugs have spark.

All connectors have been cleaned of corrosion . Coils and Injectors ohm within specs. Fuel temp sensor ohms within specs. Water and coolant sensors cleaned. I have received a detonation sensor code a few times but I figured it was because of not all the cyl?s firing.

I have to think that the plug firing order has been messed up somehow since you say the compression is ok, the plugs on the passenger side are working, and the cylinders are getting fuel. If that isn’t the trouble then it seems that the passenger side plugs are somehow firing at the wrong time.

The firing order on the is car is fool proof. Each spark plug has its own coil. The engine wire harness that plugs into each coil is laid out in a way that you can’t plug them in wrong.

Could the coils be placed in the wrong positions somehow? If the coils positions are really ok then I would have to say something is wrong with trigger signal for the firing. I guess that would come from the CAM sensor.

Even though the injector coils ohm check within specs, it is still possible that some are not closing, flooding those cylinders. Granted, that condition happening in three cylinders all on the left bank has a probability of near zero, but the wet plugs combined with the indication that spark voltage pulses exist all point to this as a possibility.

Injectors can be bench tested. It might be worth the effort. Of switch them around and see if the problem follows the injectors.

Yeah, Ive replace it with the same exact results.Its used and could be bad but I wouldn’t think it would produce the same running issues.

TSM brings up a good point about the fuel. Something I didn’t consider before. If there is a way that the fuel pressure could be too high on the bad side that would be worth looking at.

Yeah it could be. I’ve cleared the fuel rail with compressed air. they all run off the same line, do you still think it could vary that much? Do they make inexpensive pressure testers? And how would I bench test the injectors?

Bench testing injectors requires a special setup, a test bench, that provides the fuel line pressure, enables the operator to proviide the signal to the injector coil, and contains the spray. The spray pettern can even be evaluated on these stands. You’d need to seek out a place that has a test setup. Or, as I suggested, swap the injectors around left to right and see if the problem follows the injectors.

Pressure testers to test the pump and regulator are cheap. It’s just a pressure gage with some fittings and some instructions. You can get a kit at any parts store. It should be on the counter with the test equipment.

great thanks. I will give it a try.

so I found part of my problem and may need some guidance. I did another comp test. The pass side read all zeros. Driver’s side was normal. So I figured I have some valves stuck or something. So I pulled the intake manifold and t-belt off, then I pulled the cam pulleys. The Pass side intake cam sheared off the key. I have not heard and knocking pings or other bad noises while running the engine. Should I go ahead and pull the head or replace the cam/key and rotate it watching the valves to see whats happening. I know if vavles are stuck because their bent it will have to come off. I’m sure the key broke for a reason. I don’t have a lot of funds to rebult the heads.

Are both driver’s and pass side cams the same? I have a driver’s spare.

all 4 cams have a different part number which tells me they’re different.

K, thanks