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97 Altima shuts off randomly Forums > > 97 Altima shuts off randomly 97 Altima shuts off randomly
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  #16  
Old 09-30-2010, 12:00 PM
annesjn
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I measured the MAF and the voltages check out. 0.4V without the engine running. ~1.2V at idle and ~2V at increased RMP.

Not sure what's left to do. I will check the front O2 sensor to see if it is responding.
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Old 10-03-2010, 08:46 PM
annesjn
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Just thought I would recap all my investigations on the 96 Altima with 240K. I have hesitation and stalling that gets worse when the engine is hot. It it worst when I try to accelerate from stop and seems to go away at higher RPM. For the most part it idles in neutral fine and dies only on occasion when idling in drive or reverse. It is harder to start and sometimes requires I open the throttle to get it started again.

It is running lean, I know this by using the ECM Mode II diagnostic mode that shows the front O2 sensor status using the CEL. On = lean, off = rich. It hesitates wants to stall and has loss of power and the CEL indicates a lean condition when this occurs. If I pull the MAF the hesitation and stalling go away and it just has the 2.5K RPM limit due to limp mode (limits fuel). But I checked the voltage out of the MAF at idle and increased RPMs and it checks fine. I think this is because limp mode (fail-safe) dumps more gas into the cylinders(twice per engine cycle on all cylinders). The only codes it has are P0136 (O2 Bank 1 Sensor 2 low voltage) and P0325 (Knock Sensor). I think the rear O2 is due to damage from running over a truck tire on the highway, but regardless the ECM doesn't use it to control the engine.

I checked the fuel pressure and thought I had a bad regulator as it would not hold pressure sometimes so I replaced it. It holds pressure but I still have the problem. I also replaced the O2 sensor thinking maybe it was giving a faulty response (also it has at least 170K miles on it so for $17 why not, its a 1 wire). It didn't change anything.

I tested the EGR valve and the diaphragm moves freely. I also pulled vacuum from it and still it hesitates and stalls. There was a bad vacuum hose going to the EGR backpressure transducer so I replaced and no difference.

I know there is a problem with intake manifolds on altimas but I replaced mine about 2-3 years ago and the symptoms are completely different (rough idle, gets better higher RPMs rarely stalls).

I have reached the end of my abilities here and I have only two things left that I can try. About 6 months ago I was getting a misfire on cylinder 4 that went away with the EGR vacuum removed. Turned out the the manifold channels were filled with carbon so I cleaned it up and the problem went away. I didn't have a gasket at the time and just used high temp silicone to seal it. I am thinking maybe there is a leak there. However when I spray it with carb cleaner, the idle doesn't change. But I guess for $8 what not just rule that out. The last thing I want to try, due to cost is replace the MAF. I have cleaned it with spray but there is no difference. And as I mentioned it checked out with a volt meter and there are no codes for it but I figure it could be intermittent?

One last thing I for got to mention I check the TPS and get 0.4V at idle and 4V WOT with even change trough out. And I check the ECT sensor it it was within range. Also I cleaned the camshaft sensor (LED encoder wheel) about 3 years ago and checked it now and it is clean.

Any thoughts would really help me out. Thanks!
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