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1997 Altima idle/stalling problems

About a year and a half ago, my car suddenly cut out when stopped at a light.



The exact problem is, I'll be sitting idling, and if I sit there idling too long, sometimes (not always), the idle will start fluctuating, racing too fast, then dropping to too low, then bouncing back to high, and after a couple of iterations the "too low" bounce will make the engine stall. I have gotten decent at hearing the sound and throwing the automatic into park, putting foot on gas, and essentially manually keeping the car from conking out by keeping the engine racing faster. When the stop light changes, I have to throw the car into drive and hit the gas quickly to keep the car from stalling.



Once this problem has started, it doesn't usually stop. Sometimes I'll sit in a parking lot and just keep the gas peddle pressed down for several minutes, and there'll be a pop(it's not realy a sound, but I can feel the gas pedal versus revs dynamic changes) and if I release the gas pedal the car will go to an idle that doesn't require me to manually keep it going.



Since that time, this is an intermittant problem that has been plagueing me. I took it into the dealer within a couple weeks of the problem starting, and they gave me the "it's an old car, it could be anything". Gave it a tune up, replaced the battery, and replaced an engine gasket (sorry, forget exact name). It didn't fix the problem. Last December (before driving it 350 miles for holidays) I took it into a mechanic shop that a coworker had suggested. The car, of course, didn't do it's thing while they had it, so they couldn't diagnose the problem.



Luckily I live within walking distance of work, so the only times I drive the car is about once a week for groceries and once a month downtown to pay my rent.



I cannot seem to find a consistant, predictable list of conditions as to when this happens. It *seems* to happen more frequently when it's raining/high humidity, or if I haven't let it warm up all the way before taking off. Letting the engine fully warm up (as in, temp gage in the middle) is not a cure. It will still do it even if the car is warmed up all the way. In fact it's often times a worse problem if I've been driving it around off and on for over half an hour, as the conking out of the engine is NOT proceded by the revs fluctuations. I'll just be sitting at a long light, and it'll go from ~900revs down to less than 500 and boom! hello restarting the car).



When the car dies, it generally starts back up. If the stall happens right when the light turns green, it will sometimes act flooded, but I've gotten into the habit of if the car dies to just count to 5 or so before trying, and that usually does the trick...however, the start is usually very rough, as in, there is no idle, it requires me to press the gas pedal down to keep the car from dieing again.



I'm very poor, so I can't afford to just let mechanics "guess" for $500+ a pop without it fixing the problem. The car has 110K miles on it, I am the only owner, and while not a perfect good keeper, I have always gotten the oil changed and taken it in every 30k miles or so for tuneups. I definitely can't afford a new car, and picking up someone else's bad apple doesn't seem like a solution. I'd rather just fix the one I have =/
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Comments

  • edited April 2010
    It could be oily soot inside the throttle body housing interfering with the operation ot the throttle plate that controls airflow into the engine. Take off the large hose between the air cleaner and the throttle plenum (housing) and look inside. If it is dirty use spray carb. cleaner and an old toothbrush and rags.
  • edited April 2010
    A Couple Of Questions / Suggestions :

    Is The "Check Engine" or "Service Engine Soon" or other instrument cluster warning / information lights illuminated now or have they been ?

    Has anybody including the dealer ever mentioned checking for or finding any trouble or fault "codes" in the process of diagnosing the problem ? If so, do you know what they are or are they written anywhere on a receipt or anything ?

    Have you taken this car to an autoparts store like an Advance Auto Parts or Auto Zone and asked to have it checked for any stored OBD2 codes ? Many do this for free out in the parking lot. Some folks post the codes on this site as clues as to what the problem(s) might be and people offer suggestions.

    Should you get some codes, write them down and post them here in a format that looks like: PO100 or PO304, or PO136, etcetera. Maybe somebody can offer more specific ideas.

    CSA
  • edited April 2010
    The check engine light only comes on at the time of the stall, but goes away while the car is running. I tried to do the Auto Zone thing, but they said they couldn't do anything if the check-engine thing wasn't on when they did it.

    I am pretty sure the dealership did the diagnostic when I took it in, but as I said, they did not come back with any specific failures that I assume would have shown up during a diagnostic (ie, fuel pump, o2 sensor). But...I wasn't standing behind them watching them while they did it, so if you think I should get a 2nd opinion, I could probably do that. It has been 18 months or so since that test was done, so it might not hurt to get it done someplace else. I just really can't afford to be spending 100 here, 200 there, 500 maybe this might be it..
  • edited April 2010
    Unfortunately there is but a guessing game to do without codes or specific conditions.

    You do mention the possibility of moisture being involved (raining/humidity). The next time the weather is clear and dry, start it up, pop the hood, and use a misting-type spray bottle with water in it to mist the spark plug wires. Follow the wires to whatever they are connected to (coil or distributor cap) and mist that too. If you get any engine stumble associated with the misting then your problem is with whatever component acts up when misted. You can mask certain components at different times to isolate it.

    Other than that it sounds like an intermittent vacuum leak. The things that come to mind would be an evaporative emissions purge solenoid or an EGR valve that sticks open. Another thing could be an idle air control valve (IAC) that is getting sticky or has a bad connection. I'm sure there are other things. Does it ever seem to be associated with having the brakes on or off?

    For $20 you can buy a Haynes or Chiltons repair manual at an auto parts store. This will tell you, for example, where all of those components I just mentioned are and how you can test them. I would certainly check the wiring to the IAC and pull it off for a good cleaning. In addition to the manual you will need a multimeter for electrical testing. You can get these as low as $10 (though for long term utility I would spend at least $20).

    As oltimer 11 said - a cleaning of throttle body also can't hurt and is cheap and easy.

    You should also cross your fingers that this eventually triggers the check engine light - at which point the codes will point you to the diagnostic steps.
  • edited April 2010
    [resolved]
    I took the car in for a different problem (AC compressor belt/pulley was bad). This dealership was able to determine the idle/stalling problem was a leaking intake gasket. So far I have not had any problems since getting the repair, so I may actually be able to drive my car more than just to work/grocery store.. yay :)
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