Engine stalls when switched to neutral

I got a 5spd stick shift Nissan Altima 1997 with 150000 miles on it, from a friend as a gift lately. The car runs well, the only weird thing being: the engine revs per minute drop so low after switching to neutral (from any gear - be it at a low speed nearing a stop light or at a high speed on a freeway) that engine stalls. By low RPM I mean the reading on the dash going all the way down to some 0-100 rpm. It stalls more readily when cold. When the engine and weather are warmer it happens much less frequently although I see the rpm reading doing the same. It just feels like hot engine sustains better. With warmer weather I started running A/C, which seems to help somewhat. I assume it is because the A/C power demand offsets the idle speed. If it happens at a stop light I can always start it back fine and it will not stall just idling no matter how long (likewise when I first start it - it can sit and idle with no problem). If it happens in motion, putting it back in gear starts the engine. So it seems to me that the act of switching from gear to neutral causes stalling.

Unless someone tells me about an inexpensive service or DIY way to fix this, I will continue running it as is because I got the car for free and nobody knows how long it will last, so investing a lot in it does not make much sense to me.

The only thing I always do (myself) on all my cars is very regular oil changes (drain, put 2-3 qt fresh oil, run for 10-15 min. for extra rinse, drain, change filter, put new oil).

I have not had the car for long enough to report the mpg value but it seems to be reasonable (>25m/g, maybe higher). It definitely needs an oil change, which I am going to do right away.

Thanks a lot for your advice, tips, and any questions in case there are details you want me to add or clarify about the car and the symptoms.

I did search for similar discussions. There are some about low idling speed but they do not address a manual transmission, not switching from neutral.

If it has not been done recently, have the throttle body and the idle air control valve cleaned. At the same time have the throttle position sensor checked to see that it is operating to specification.

There is a Technical Service Bulletin addressing the base idle and timing service procedure that may be appropriate. However, this might take a trip to the dealer $$ unless you can find an independent mechanic who has access to the TSB and the appropriate tooling.

Hope this helps.

Does it do the same thing just putting the clutch in, or do you actually have to move the lever into neutral?

Frankly, I have never paid attention to this, so can’t tell right now. I will try just pushing the clutch in and will post the result tomorrow (Sunday). Thanks.

I know from my friend that they did take the car to a mechanic last year when the problem first occurred. He says, the work was done on somehow adjusting the idle speed. That’s as much as I could get out of him, so don’t know what exactly was done.

Thank you for the advice! Unfortunately for you, it prompted further questions.

  1. If I have everything that you mention done by a mechanic, how much approximately am I looking at? 2. Would it make any sense or save any money to do those things one by one? 3. Is a TSB different from an Auto Repair Manual (those books published by Haynes and others)? 4. I have also found this information on the web:
    Would you trust their description to do the job of cleaning the throttle body? Thanks for answering any of these questions!

Putting the clutch in does it without me having to move the lever. Thanks for any help!