# Altima bucking & stalling, lack of power



## faraway64dn (Apr 21, 2012)

Hello again,

My 1996 Altima GXE (AT) has some serious troubles, and neither Nissan nor my local mechanics can figure it out.

My Altima is misfiring whenever I accelerate. A week ago, it would completely stall whenever I accelerated while engine RPMs were low.

In this order, I have: replaced valve cover gaskets (spark plug wells were filled with oil), replaced ECU (MIL was flashing but no codes stored), changed the fuel filter, cleaned EGR valve, changed the distributor, and replaced plugs & wires. Per the advice of a friendly gentleman on this forum, I also sprayed carb cleaner around the vacuum lines to check for leaks (supposedly, an RPM spike indicates a leak). I got nothing.

I'm really running short of ideas here. A multimeter indicates the wires are fine, and although I am hearing what sounds like a misfire, the plugs don't look crappy -- which I would expect in the event of a misfire. Fuel pressure tests come up normal, according to my mechanic. 

I'd welcome any suggestions


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## rogoman (Dec 16, 2004)

Since you replaced the ECU, are you now getting any fault codes? If there are fault codes, what are they? What were the actual fuel pressure readings?

Several things to check:
- Bad O2 sensor.
- Dirty fuel injector(s). Run fuel injection cleaner through system.
- Intake manifold vacuum. The proper way to check the intake system for a vacuum leak is to attach a vacuum gauge to a full vacuum source. With the motor 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. Also check the intake plenum bellows at the throttle valve and at the MAF for cracks or loose clamps.
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Here are some vacuum gauge readings and their indications:
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Low & steady ---------Late ign timing/valve timing,
low compression

Very low ----------- Vacuum leak

High & steady ------------ Early ign timing

Intermittent fluctuation at idle ------------ Ign miss, sticking valve

Needle fluctuates as engine speed increases ------------ Ign miss, blow head gasket,
leaking valve or weak valve spring


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## faraway64dn (Apr 21, 2012)

Success at last! I want to follow-up and explain how my problem was resolved.

1st and foremost, my original ECU was not faulty. I'd accidentally locked it into trouble diagnostic mode by over-torquing the switch on the side. After fixing that, I got codes: (misfire on cylinder 3) P0303 and (camshaft position sensor) P0340.

The CamPS is on the distirbutor on the 1996 GXE -- it's what the harness plugs into. I was skeptical, because I'd already replaced the distributor with an aftermarket brand. A trusted mechanic told warned me that its very common to get a bum aftermarket distributor. 

So, I ordered a different one. I set my engine at TDC on the advice of a fellow from another forum: you just take out plug 1, stick a long, clean metal rod or screwdriver down in the piston, and turn the alternator pulley to move the crank shaft. First, I measured the piston's apex by holding a ruler against my screwdriver (so i could see how far it would up travel). Once I knew, I put my hand over the well and cranked until I felt resistance of air pressure, which meant the piston was on the compression stroke. When it reached the top, I put the new distributor on and voila! The car runs great! 

Some stuff I learned on the way that might help others:
1) I first replaced the valve cover gasket, b/c the wells were filled with oil. Pay the extra $10 to get a $30 gasket from Nissan -- the Nissan gasket has little bumps that help it stay seated. The one I got from the autoparts store kept falling off while I was working with it, and I ended up having to replace it anyway. 

2) Aftermarket distributors are a numbers game!

Hope this helps someone, and thanks to all who tried to help me


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