# 96 Nissan pickup 2.4L violent bucking



## Houstonlh (Oct 25, 2017)

Hello everyone, I had a weird problem with truck on the way home from work today. It was driving fine at first but i started to notice the truck losing power and each time I would shift into a new gear it would jerk, so I stop at a stop sign and as i take off the truck has no power and then all at once starts violently jerking so i pull off on the side of the road and sit there and minute and try giving the truck gas in neutral, as im giving the car gas it revs then drops then picks back up and drops again and then stalls. 

As I call for someone to come and rescue me I try and start the truck again it just clicks, and somehow the the battery's dead. I get a ride home and decide to go tinker with it to see if maybe it had run out of gas or something because none of the gauges work, I put 5 gallons of gas in, jump it off and cranks up and seems to idle fine but as soon as i take the cables off i noticed a change in the idle. I hopped in the truck and tried giving it gas again and same thing, the truck acts like its only getting pulses of fuel and dies again. 

So here I am planning to have a tow truck come pick it up tomorrow but the curiosity is killing me as to what this problem could be. I checked the codes and had a code for an o2 sensor and that was it, not sure if that could cause a problem like this. I was thinking it could possibly be the fuel pump but that doesn't explain why the battery would die. I just had a new battery and alternator put in last year but the way things are made nowadays there's no telling if its the alternator or not, I'm not even sure if a bad alternator could cause such problem. So if anyone has had any similar experiences or have any insight on this situation it would most helpful and give me an idea of what I'm looking at. Thanks in advance!


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## rogoman (Dec 16, 2004)

One of the first things to do is perform an ECU code readout with a portable scan tool to see if any fault codes are set. The tool can be purchased at most auto parts stores. The condition you're describing can be caused by a marginal crankshaft position sensor or a camshaft position sensor. If you're buying one or both of them, buy only OEM units from a new car dealer. Don't buy aftermarket types; they've been known to fail in a short time; some are even DOA.

To properly diagnose dirty/leaking fuel injectors, they need to be remove and tested on a flow bench tester. You can also do a quick leak test by teeing-in a fuel pressure gauge to the fuel rail input, then turn the ignition switch to the "RUN" position without starting the engine; make sure to pinch off the return hose on the pressure regulator when doing this. If the pressure drops off rapidly, one or more injectors are leaking.
How long have you had the old spark plugs? If they are very old, then it's time for a set of new ones.

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Irregardless of what fuel pump you're using, the pressures need to be as follows:
Tee-in a temporary fuel pressure gauge to the fuel rail input. The readings at idle should be approximately as follows:
- with vacuum hose connected to the fuel pressure regulator: 34 psi
- with vacuum hose disconnected from the fuel pressure regulator: 43 psi

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There may be a major vacuum leak in the intake system. Use a vacuum gauge for good accuracy; most auto parts stores sell vacuum gauges. To check the intake system for a vacuum leak, attach a vacuum gauge to a full vacuum source, usually somewhere on the intake manifold. With the engine fully warmed up, the reading at idle should be 18 - 20 InHg. At 3,000 RPM, it should be around 21 InHg.

If readings are under 18 InHg, check the intake manifold nuts to make sure they are tight. The gasket may have failed; spray a water mist at the gasket to see if the gauge reading changes. Also check the intake plenum bellows at the throttle body and at the MAF for cracks or loose clamps.

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The CAT may be plugged up. The easiest test for converter plugging is done with a vacuum gauge. Connect the gauge to a source of intake vacuum on the intake manifold, carburetor or throttle body. Note the reading at idle, then raise and hold engine speed at 2,500. The needle will drop when you first open the throttle, but should then rise and stabilize. If the vacuum reading starts to drop, pressure may be backing up in the exhaust system.

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Your other problem with a dead battery could just be due to the battery getting run down from repeated attempts to start the engine. A properly working charging system puts out about 13.2 to 15.0 volts, but this is a general spec. and the factory service manual (FSM) should be referenced for the correct charging system voltage specifications for a particular vehicle. A battery should have a static charge of 12.2-12.6 volts. If a battery is not good, the charging system may not be able to charge properly. If a vehicle is not charging properly and the battery is good, first thing to do is to turn the ignition switch key to the "ON" position and make sure the charging system warning light is operating. If the bulb is burnt out, the charging system will not charge. If the bulb is OK but still does not illuminate, the circuit must be tested. If the warning lamp does illuminate, then the next thing to check is to make sure the circuit between the battery positive post, or fusible link, to the connection in back of the alternator is good. On Nissans, this will be a thick (approx. 10 gauge) white wire to the "BAT" post on the back of the alternator. It's not uncommon for this wire to get corroded and burn up, creating resistance in the circuit. So, before assuming an alternator is bad, make sure this circuit is good and battery voltage is getting to the alternator. It's also important to make sure the alternator belt is tight and not slipping and the battery connections are clean and tight. Also, it is NOT a good idea to disconnect a battery cable on a computer controlled vehicle while running to test the alternator. This is a good way to damage an ECU. When a charging system is not charging, or overcharging, a lot of "strange" things can occur. It's not uncommon to see a multiple of stored trouble codes in the ECU memory. So, whenever a car is setting a multiple of trouble codes, idling funny or stalling, or anything out of the "norm," test the charging system before you start pulling hairs!


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## jp2code (Jun 2, 2011)

Your alternator went out.

The engine kept running as long as the battery had enough power to run the fuel pump and injectors.

Now, your battery is dead, too.

Buy a new (not a rebuilt) alternator and a new battery.


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## smj999smj (Jan 1, 2006)

I'm leaning towards a charging system issue as well. I would first address the battery by charging it a re-testing and, if necessary, replacing. Once the battery is known good, test the charging system and make sure it's between 13.2-15.5v. A charging system that is charging too low or too high can cause all kinds of issues and can also false-trigger codes.


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## Houstonlh (Oct 25, 2017)

Hey guys update here.

I got the truck towed to the garage that originally replaced the alternator.
I told them what happened and that I thought the problem was the alternator, they told me if it was they would honor it and replace it for free.
But they also told me that they were backed up and they didn't know when they could mess would it but said it would be within two weeks.


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## smj999smj (Jan 1, 2006)

I understand that shops can get busy (I've worked in them), but two weeks to check a charging system?? Makes me glad I can work on my own cars!


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