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At a stop sign I need to put the car in neutral to keep it from jerking and idling rough. There is a popping or backfiring that comes out of my afm when taking off from a stop. It is worse right now due to the gas additive that is out. Also for some unknown reason I have had 4 out of 6 sparkplugs break off at the tip inside of the plug wire, ever heard of this. This car has a lot of problems.
 

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I will try to answer both of your posts. First, buy a factory service manual (AKA: a FSM) You can get a cd-rom version from www.zcarcreations.com. All the info you need is in the engine fuel section.
Look for any vacuum leaks. Check the air flow meter boots for holes/cracks. Trying to seal them with silicone is rather useless and makes it a crappy ghetto repair. Just replace them. Motorsports has them for a little over $20.00. Also check all the vacuum lines on the engine for cracks, dry rot, ect. You can replace most of them with 5/8" heater hose, 3/8 vac line, ect.
Get new spark plugs and wires.
Clean all the FI sensor connectors. Pay close attention to the ECU connector (located in the kick panel on driver side). Pull the connector, clean and reinstall. Clean the water temp sensor connector on the thermostat housing (not the single bullet connector that feeds the dash temp gauge).
Adjust the TPS (throttle position sensor or as the FSM calls it, the throttle position valve) per the FSM instructions
Test the afm, water temp sensor per the FSM test procedures. You will need a digital multimeter... Keep us posted.
 

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You should first check your fuel pressure. A lean fuel condition will cause the intake backfire. You may have a oxodized fuel tank or other fuel system resriction. I have seen this condition on many Z cars of all years. I have seen Nissan Dealers replace all kinds of exspensive components trying to fix the symptoms you describe. If your fuel pressure is low I would start at the tank and work your way forward. Save your self a lot of money and time and pull the fuel tank inspection cover inside the rear hatch and pull up the sending unit, you will know right away if this is the problem. If you see black or red particals or sludge drop your tank, take it to the car wash, high pressure wash it, wire brush it (if you have small arms and the right brush you can get to the whole surface of the inside of the tank), power wash it and repeat the wire brushing until you see clean surfaces inside the tank. When I did my last tank it looked like the inside of the tank was rusting out, but after the above procedure it looked like new again. If this is what you find in your tank make sure you add a couple of cans of Heet to you first fill up (it will protect your tank by removing moisture and protecting the steel) and change your fuel pump screen and fuel filter. My car was doing what yours is so badly that it would start and idle while popping through the intake. I could drive about a block on average and then it would die. If I let it sit a few minutes it would start up again. A few times it would run good for 2 miles and then do the same thing again. I wnet through all the components and test before I had the insight to check the fuel delivery system. Good luck.
zbyter
 

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Re: broken spark plugs...

Just a couple of thoughts on the spark plugs. 1)Perhaps the heat range is wrong and causing an extreme heating situation and causing them to crack off. 2) The lean condition (either air leaks or not enough fuel covered by johnb510 and zbyter) is causing the overheating of the plugs and cracking. 3) Poor installation/removal technique of the plugs. Typically, #3 is the cause of broken spark plug insulators on the outside of the engine while #'s 1 and 2 would be more likely cause of broken insulator tips inside the engine. Just for info the spark plugs should be TORQUED with a torque wrench to about 14-15 ft/lbs and no more. If your wrench is slipping off the spark plug this can cause the outside insulator to get cracked.
 
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