20 Most Recent 1990 Nissan 300ZX - Page 2 Questions & Answers

first check the condition of the battery in the key Check by using the extra key. Next run the fault codes.

Check the power transistor unit (the small black box on the front of the engine, passenger side, slightly beneath the main black intake hose coming to the intake manifold). It has six or seven wires coming in one side and out the other. That part was the one warranty recall for the Z from 90-96. I'm not sure what year yours is since the question is listed as a generic 300ZX question, but the recall affected 1990 models and a few early 91s. The PTU was redesigned with a heat sink to keep it from overheating (the main reason determined to cause the failure). This is the unit that drives the signal to the coil packs to fire the plugs. If it dies, you'll have no spark and the car won't run unless it decides to revive itself or you change it. If that doesn't fix the problem, I'd look into the CAS (metal circular sensor, front of the engine, driver's side, one harness plugged into the side) - that is the cam angle sensor and can cause you to lose ignition as well.

sounds like the injector on time is too long. you may have to see why they are open too long. the regulators that you put on where they new or used?

Possibly a computer (ECCS control unit) malfunction, but first check the white/black wire going to each injector. All should have power on them with ignition key in on. This white/black wire comes from the computer's pin # 58, then is spliced to all 6 injectors. If no power to injectors, check the wire continuity from the ECCS' #58 pin to the injectors. The ground wire from each injector also goes into the control unit, but individually, so that the control unit may ground the injector circuit and cause pulse. If the wiring is good, no breaks or shorts, it may be a computer malfunction, but first find out if the variable valve timing affects injector pulsing. I don't know anything about it, but you have 2 VTC (valve timing control) solenoids, one for each side of the engine. Both are located near or on the firewall behind the engine, near the middle. Looks like 3 solenoids there, the middle one is the EGR solenoid, and the VTC solenoids are on each side of the EGR solenoid. Best I can do from a very poor wiring diagram I was looking at. You checked for spark, but did you check on all six plugs for spark?

There is a leak, possibly a brake line or internal leak in Master Cylinder.

Sounds like a vacuum leak. If you or someone you know knows about vehicles you can deduce the problem, otherwise you may want to go to a mechanic who understands vacuum leaks.

The most probable cause is a cylinder temperature sensor. It's located on the right side if you are faceing the engine. Look at where you put your coolant in, follow that housing down on the right side and look further down near the bottom of the front of the cylinder head. The color of the sensor will be yellow. The computer is looking for a certain resistance value which makes it change the pulse width of the depending on the temperature of that sensor. Nissan technicians do what is called a pinout check at the harness which plugs into the computer, using a digital volt ohm meter. You can get the information off the internet or go to a book store (Barnes an Nobel) and they carry a wide variety of auto repair manials. Haynes typically publishes manuals on different makes and model cars. Each manual is specifically for the kind of car you are driving and usually will cover several years of your model car. In those manuals they will show instructions most of the time on how to do things on nearly everything on the car except body. The resistance values for that sensor and where to check it should be in the book. I can't give you a specific value because engines get hotter when you initially shut them off and some cars run hotter than others, consequently the values will not be the same ubless the cars are both within a close temperature range of each other. The connections can even be corroded which will cause the problem. Be sure to check the plug as well as the sensor for corrosion..SCRAPE THEM CLEAN and put a little "dialectric" grease in the plug before you snap it into place.There is a box on the right hand inner fender which has a labeled cover The head light relays are in there. I think the efi relay is in there and one or two more, I can't recall and at hom with no references in front of me. To make matters worse, I have Parkinson's disease which can affect memory so what I use to be able to rattle off, I can no longer do unless it's an old 240Z or something in that era. I'm in my 60's and have worked for and witth Datsun/Nissan. (as I refer to it) since 1968..I was talking about the relays. Some of them are the same and will switch out. if you see a relay that looks the same as the EFI relay, swap them and try to start the car. I hope I might have been of some help.Right now, it's early in the morning and hard for me to think clearly. If I have any other ideas, I will surely add them.

Does it make noise? Squealing, etc? Is the fluid low? Tire pressure correct?

My first suspicion when I read this is that your air conditioner pump has seized..... This very quickly burns the belt in two... Either that or your alternator or water pump or power steering pump... You have to find out what doesn't want to turn..

try changing the scv suction control valve

Check Fuses and Bulbs . I had a switch wear out once on a Chevy Blazer .

The reason it's stalling out is because of the adjustments you made to the CAS and TPS. You need to reset the CAS where it was, since when you rotate this sensor, you change the ignition timing. As for the TPS, that also needs to be reset to how it was. The way to adjust the idle on this engine is with a screw on the idle air control valve (IACV). At the back corner of the engine, on top on the driver's side, the IACV is bolted on. If you crouch down next to the driver's fender and look straight in at the IACV (with a flashlight) you will see a screw recessed in there, with the head pointing toward you. That's the idle adjustment screw. With the engine running, AFTER you have reset the CAS and TPS, turn this screw until you are able to set a warm-engine idle of roughly 750 RPM. Messing with TPS voltage and ignition timing is a sure-fire way to stall or blow up your engine.

any noise from gearbox when you engaging clutch when engine is running? Check for oil as well. Firstly I suggest to drain oil out and check for particles in the oil, synchros could be damaged