Engine Stalls on 2001 Nissan Altima

The engine of my car stalls at various phases. After I start, the engine stalls sometimes. When I change gear, the car stalls sometimes. The most commom stall I have come to notice in the last days is when coming to a full stop. At the beginning I thought it was due to LOW RPM, but today when I was driving it, it idle really well. When I started to put gas (accelerate), the car would hesitate. If I let go of the gas pedal, the car would stall. Sometime when going about 45MPH, I can feel the car hesitating to maintain RPM. The mechanic could not find the problem. I change spark plugs, air filter, fuel filter, clean the throttle valve. The mechanic checked the oxygen sensors, and other sensors, including fuel pressure, and never found the problem. Please help, thanks!

by in Wilmington, CA on October 09, 2010
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2 answers 5 comments
ANSWER by , October 09, 2010
Does it ever runs good, or this problem is there all the times? Is the Check Engine Light (CEL) on? Any trouble codes from ECM? Is the idle always low? Did your mechanic checked the EGR valve? It may not close correctly. Zee
COMMENT by , October 09, 2010
Mechanic did check EGR valve. No check engine light on, no codes. It runs good for 5 min and then it starts giving me problems. The always is sometimes low, not all the time. The mechanic "supposly" check everything there is to be about this problem and found nothing.
COMMENT by , October 11, 2010
Was the problem there before you changed the filters and spark plugs? Anyway, I'd clean and test the Mass Air Flow Sensor,scope test the Throttle Position Sensor, the Cam and Crank Sensors. Is the problem relates to cold/hot engine, bumpy roads, rain, etc... did you noticed? Zee
COMMENT by , October 11, 2010
The problem was there before I did that. I will clean/check the sensors. The problom is there randomly;hot/cold engine, dry weather, normal roads, and I currently live at a 5000 ft. elevation. I have been living here for a while tho, so I dont think altitude is a problem.
COMMENT by , October 11, 2010
So you live a bit high? Do you drive up and down frequently? If the Absolute Pressure Sensor won't respond to the changes correctly it could cause this problem. Since on higher altitude there is less oxygen in the air, also the manifold pressure changes so the ECM has to correct the air-fuel ratio accordingly. The bigger problem: it's built into the ECM, not a separate part. It would be good to monitor the live data and see how the APS responses. Zee
COMMENT by , October 11, 2010
Cool I will do that. I dont drive up and down frequently, neither I drive the car for many miles. I drive from home to school, school to home almost every day (5miles each leg) and the fastest I go is 45MPH. Since my car started giving me problem, I havent driven my car during the weekends. But I will monitor that, Im hoping its a bad sensor, but this is a very random problem; that is the worst part
ANSWER by , January 30, 2011
change the spark plugs and wires. That should fix it.