Question about 1991 Nissan 300ZX
My 91 nissan 300zxtt runs real ruff like its running on 5 the water pump just gave uo and now the only way to get drive is to ring it out..whats happening to my baby and how do i fix??
Tonyautos: CAUTION!!!!!!! A VG30DET is a very tight tolerance engine and not tolerant to dirty motor oil, poor quality oil, cheap oil filters, overheating and/or abuse from trying to run it when it is not running properly.
It can be pushed hard and to the very limits providing things are mechanically in order.
First thing which needs to be done is establish the severity of the water pump problem. If the pump failure is such that coolant is running out as opposed to a slow drip. If the bearings have failed and the pump shaft is doing more than rotate, it has a lot of axial play. The pump bearings are noisy. Any one of those symptoms are grounds to first replace the water pump before attempting any further diagnostics. Note, a more seasoned tech, might further the diagnostics even with these conditions, however, my instructions to someone inexperienced, is to avoid any possibility of damaging the engine.
Making the assumption that the pump passes minimum standards and you top off the cooling system, Now I am also going to factor in that most week end warrior does NOT have a compression tester or other special tools, so the methods I am giving are based on using the basic hand tools most people have.
Remove the ignition coils from the tops of each spark plug. An 8mm socket to break the bolts loose and a #6 phillips screw driver to remove them quickly. The harness attaches to the ignition coil by means of it snapping in place. It can be released by depressing the latch at the center of the harness connector right where it pushes into the coil connector. Just pinch it, rock it side to side a little as you pull it backwards and it should come right out. Now you can lift the ignition coil right off the top of the spark plug. Look carefully at the boot which is at the end of the plug wire. Check it for cracks and signs of high voltage arcing. Make sure it goes back over the tip of the spark plug when you reinstall the coil, otherwise it will arc to the sides of the cylinder head causing a misfire. Remove all the spark plugs with a 5/8ths spark plug socket and check them for color. CAUTION!!!!!!! MAKE SURE THERE IS NOTHING ANY WHERE NEAR THE SPARK PLUG HOLES WHICH COULD ACCIDENTALLY FALL INTO THEM! IF SOMETHING FALLS IN THE HOLE AND GETS IN A CYLINDER WITHOUT YOU KNOWING IT AND YOU CRANK THE ENGINE>>>>: CAN YOU SAY "TRASHED MOTOR?"
Also if there was a possibility that the engine was over heated, check the plugs for signs of water. You are looking for uniform colors from all the plugs. If you find one or more which are different, it usually means the the cylinders which those plugs came out of, are the ones which are most probable in causing the symptom.
If you find water on any spark plugs, leave them all out and after covering the fenders and nose of the car, crank the engine and look for water or water vapor being pushed out of those cylinders.
If you see vapor or water spray from any cylinders, the game is over! The repair is in all probability well above your technical skill levels and you must make a decision as to whether you can afford several grand to put into repairing this engine, providing there is no damage beyond a blown head gasket. Usually it is a good idea on the engine to do both head gaskets and a few other things on it due to how labor intensive the job is.
The other option is to buy a used engine from a salvage yard or engine supplier. Sometimes the places that wholesale engines to the public, install them for a package price which is a good deal...BUT BE CAUTIOUS! Some of them are DEVIOUS! Check with the BBB. Not having a history with the BBB doesn't guarantee you woun't get stung, but it cuts your chances in half!
Getting back to the subject of checking your engine out:
OK, the last test has given no signs of coolant in the combustion chambers. Open the oil filler cap and look on the under side of it.
Another typical sign of a blown head gasket is water in the oil.
You will see a deposit of a kind of light foamy mixed oil and water residue in the cap. Almost like a milk shake. If you see this, hang it up, the same is true as I had mentioned above.
Assuming no signs of water are in the oil, you can move on to the next step. Look at the air intake, check it for cracks, tears in the hoses or hoses which have come loose.
If you find nothing, put the spark plugs back in, reinstall the ignition coils. Start the engine and listen for the misfire and or look for the rough idle. (if you have found problems, these must be fixed, because they will affect the idle.)
With it idling rough, disconnect the harness from each coil, one at a time, looking for the following. Any cylinder hitting, when you disconnect the harness, the engine speed will drop noticeably and may even want to stall. Quickly reconnect it. If you find a cylinder which doesn't seem to respond much or at all to your disconnecting the harness, then, you have isolated the cylinder.
NOW, you need to determine if the problem is the coil.
Swap the coil from the cylinder which wasn't hitting to one which was and recheck for the rough idle, if the problem cylinder moved with the coil you transferred, the coil is the problem REPLACE THE COIL! If it didn't, then the nest step is to swap spark plugs and try again. No change?
Next step is to listen to the injectors. Get a long screw driver if you can get your hands on one (long meaning 2 feet, but a slender shaft, like the # 6 phillips). If you can't find one, find a reasonable facsimile. With the engine running, Put one end to the base of an injector of a known working cylinder and put your ear "ON" the other end the the screw driver. Listen to the clicking the injector is making. Now place the screw driver on the base of the injector of the dead cylinder and make a comparison. Does it sound the same? NO? Then the injector either is bad or the injector is not getting a pulse to trigger it. This is about as far as you can go without spending money on test tools or things to make test tools.
So, I hope I have shed some light on your question and might have given you some means of making a sound decision as to the avenue to take on getting your car repaired or tackling it your self. Let me know if I can help you any further and possibly give your opinion on my answer as input to FIXYA.
Posted on Apr 23, 2009
The same happened to mine... i hope your problem is different... try unplugging the coil packs one by one while the car is running. if you find a cylinder that is "dead" do a compression test on all cylinders. a severe loss in compression can cause it to seem like its running on 5. the water pump isnt a terrible thing to replace but its not for the faint of heart.
in some cases the spacer between the piston rings can disintegrate and cause a massive failure with a possibility of scoring the cylinder wall. at that point its easier not to mention cheaper to just replace the engine. let me know what you determine
Posted on Jul 08, 2009
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Posted on Jan 02, 2017
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