Hello all,
My Daughters 2002 Altima randomly dies when idling. "No Codes " I am a bit of a gear head and have done the following in an attempt to solve the issue:
Cam & Crank position sensors
Both o2 sensors
Fuel pump
Throttle body
Mass air flow
Fuel cap
Torque converter (dealer said it was randomly locking up and killing motor at idle according to there technician.)
Computer idle relearn and additional computer programing by certified technician at dealership.

Only parts not replaced are the injectors and computer. Any idea what could cause the car to randomly die? Always starts right back up and only happens at idle when driving. Car runs awesome otherwise. Have heard of this happening to other owners but no remedy.
Could this be a transmission issue?
What causes the torque converter to lock up? Could a lock up sensor be bad or failing causing it to lock up at idle?
Thanks for any and all help!
ED.

Hi and welcome to NICO Club!

I would have guess one of those cam position sensors off the top of my head, but still would go through the FSM for all diagnoses steps before buying parts. Here's a link to the FSM. The EC chapter should have stuff for diagnoses including steps for non-code type issues (see page 40, 89, 130 and similar). Also, when you replace some parts on the newer cars, you have to do the relearn procedures (accelerator pedal, throttle valve and idle air volume are three to do). Did you do any of those?

http://www.nicoclub.com/FSM/Altima/2002/

Please let us know how it goes.

I simply bolted on the throttle body and maf sensor then took it to a mechanic where he said he would have to do a relearn for the throttle body. The car still stalled so he had someone come and reprogram the computer. That technician said he found no hard or soft codes and reprogrammed the computer plus an idle relearn. I ran some seafoam through a vacuum port and then some through the tank. The car runs much smoother but has still stalled. Could there be a relearn that they may have missed? I have been using crank and cam position sensors from Autozone. They gave me new ones under warranty but that did not change anything. Should I try a different (better) Brand? Sometimes the car begins to stall (stumble) but pulls itself out last second. Could it be the computer of fuel injectors? Only things I haven't replaced.
Thanks again for your time and advice!

Well, since you have time to try things, do all three of the relearns I mention. The instructions are there for you in the FSM, EC Chapter, Page 49. It's free! Then do some test driving and see if anything has changed for the better. Please let me know.

Possible momentary erratic vacuum leak. This supports the idea too...

'Sometimes the car begins to stall (stumble) but pulls itself out last second.'

The PCV valve must be open and working too, it supplies part of the idle air.

A TCC trying to lock at idle should produce some sort of chassis shock one may be able to feel in the drivetrain, like dumping a clutch on an idling engine.

Could be a momentary ignition issue too.

Had to buy my daughter another used car. Could not send her to school with the random dieing issue. I guess I have inherited the altima now for my personal use. Have yet to perform the relearning steps described by centralcoaster. Will do so once the weather warms a little.

Thanks for responding amc49. I will check for vacuum leaks. Dealer said he did a smoke test and everything looked fine. Not sure I trust their findings though. If the TCC refers to the torque converter I just replaced it. The dealer told me it was locking up at idle and killing the motor. Cost me $700 for a bad diagnosis. I noticed that there are a lot of nissan owners experiencing the same random dieing issue. No one seems to have figured it out and the manufacturer claims no known issues or recalls. Called a company that rebuilds auto computers and he told me to unplug a sensor to see if it throws a code. If it does he believes it is not a computer issue but if it does not obviously the computer is at fault. Going to do that now. Will let you know if I figure it out. Friend seems to think it is injectors??? I don't see how? Runs awesome off idle and wouldn't a faulty injector throw a code? Thanks All!

Well, there is a quick check for injectors. Each injector has a plug with two prongs. WITH THE ENGINE OFF - You unplug it, and put a voltmeter set to Ohms resistance (omega symbol, 20k) onto the two prongs of the injector. Then you measure the resistance. All four injectors should have roughly the same resistance number. When you get time, do that and post back the numbers. If one seems way out, you can notate that, run the engine a bit and test again later (engine off for this test, no keys necessary). The relearns can be done in the garage I think. Read through them before trying. The third relearn has two sets off instruction, one for with a consult (which you won't have) and one set for without, so skip to the without instructions. It also creates a diagnostic situation that may give you further information if there is a persistent issue.

If engine runs anything like crap before dying or just running like crap at idle with no dying and then seems to run fine higher up and under load then a vacuum leak. The leak ceases to be a factor at higher overall A/F amounts. Vacuum leaks depending on the configuration can come and go all day long to often not be a problem until it happens again. A vacuum leak is the single most common bad idle and dying issue that most cars of all brands have today all added together.

Older spark plugs with too wide a gap from wear can fault momentarily as well. If coil on plug ignition the connection to plug can deteriorate at well.

An injector can do it as well. They will tend to run better higher up in rpm, idle is the point at which they really have to be dead concise as to fuel amount since such small amounts are required then. You can mis-spray fuel at higher rpm but the other cylinder outputs tend to cover up one that is missing part of its' fuel at least until the bad one gets lean enough to begin to misfire.

If the idle simply drops too fast the dropping engine inertia can even kill one but commonly the idle control lets them drop slower now to reduce emissions, any errant control there could do it.

There are at least 50 different reasons that an engine can die at idle and more if one thinks about it, why there will often never be solid exact reasons why many cars flaw in what seems to be the same way.

TCC = torque convertor clutch. More commonly they show issue at braking when they refuse to release rather than in a pure idle state.

Part of looking at this problem will be verifying the stall or stumble type, as in does the engine seem to be running correctly at the exact time and simply pulled down to die (convertor clutch issue, there is no misfire there) or does it seem to be missing part of its' power as in misfiring or lumpy running as in all cylinders not working at once like they are supposed to be (ignition or vacuum leak or injector) just before the die. One doesn't get much time to guess at that since the engine tends to die pretty quick, and it can be very hard for people to separate the two conditions anyway, most simply seeing it's not running right and nothing more. Why one needs a well trained ear on that.

May need a better OBD scanner. 'No codes' simply means that there is no hard fault present at the time the codes are checked for but ECMs now tend to log any soft (temporary) faults as 'pending' codes, meaning ones the ECM has flagged but hasn't determined to be a hard fault yet. Depending on the software they are held for a while in memory and can be read as transient events with better scanners, and they reset after a certain period if the ECM determines the problem is no longer there. The software writers had to provide for that now as any engine even brand new can spout errors in running left and right but not serious issues and the ECM weeds that out. Or else the number of people bringing back cars for 'new car warranty work' would smother the dealers.

Soft fault = one that happens and then problem is gone, say, a slightly sticky sensor that day.
Hard fault = one that is a pretty much solid fail and present at the time codes are read.

I took the car to the Dealer and they ran a scan and told me they saw no hard or soft codes. They kept the car and drove it with a scanner (I'm guessing) hooked up . The car did die and they told me the converter was locking up and knocking down the engine. $700 and a new converter later the car died again. Sent the car to a programmer that hooked his laptop up to the computer and he saw nothing irregular as well. He did an idle relearn among other things and the car still randomly dies but only at idle. It just stumbles and cuts off? Sometimes it catches itself and returns to idle. Also worth noting is the idle is never the same. Sometimes smooth, sometimes a little rough and sometimes Choppy. Off idle the car is smooth a silk. Is there a solenoid in the trans that could be bad and telling the converter to lock up? I also noticed that if I remove the gas cap while the car is running it makes the car die? Any possible relation to my problem? Thanks Again all! Ed.

Seeking idles are often vacuum leaks. Gas cap is related to the EVAP system which could affect fuel pressure I guess. Since your hunting around, look into those. Vacuum leak testing methods are all over the internet. For the EVAP system inspection, check out that EC chapter and diagnose the various EVAP things. Also, in the FSM, there's a list of symptom diagnoses for things that might not throw codes, but affect your driving. You could look at that chart and it will give you things to investigate.

Were your injectors good? Have all the relearns been performed? (I don't think it's a relearn issue at this point, but you'll use those if you do actually get to repair or replace something.)

You lose any soft codes when you do any sort of relearn involving wiping the computer FYI.

If you have a temporary evap system leak then find the purge solenoid for it under the hood somewhere and then yank the hose that feeds from it into manifold and plug both holes. You'll set an evap code of course but it can be wiped later. Drive car and see if the issue goes away, if in the evap system it should.

Thanks for the many Great suggestions. I printed out a bunch of good literature from the manual that centralcoaster referenced. I am also going to try amc49's advice and unplug and cap the purge solenoid and manifold port. Hoping that I will figure this out soon??? Will post all findings. Thanks! Ed.

Hello Again,
I disconnected the purge valve and capped the manifold and purge valve fittings. I have been driving the car for over a week and the car "Has Not" died since I did that but it does have a rough idle. Anyone have a suggestion as to what part in the evap system could be causing the random engine dying issues?
Thanks again for everyone's help! I think I'm getting close to a solution! :-)
Ed.

Is it still having a CEL or have you cleared those codes and started over? With the bypass helping, I think that means something is up with the purge solenoid or the lines to/ from it. I'm not totally clear on it without looking at the FSM closer, but amc49 should have some follow up for that bypass test you did. I might have missed any results for vacuum leak testing on the intake manifold side of things. What did you do for that?

What is CEL again? I had no codes until I disconnected the evap system. It has a code now but the car is not dying anymore. I will look at the service manual and see if it gives me an idea what the problem could be. I believe the dealer did a smoke test for vacuum leaks but did not find anything. Now that the weather is warming a bit I'm going to get after it again and see what I can find. Pretty sure its in the evap system somewhere??? Going to check the resistance across the terminals of the injectors as well. May have something to do with the rough idle? Any more suggestions are greatly appreciated!
Thanks All!