HELP...Don't know what else to do
 

I have a 1996 Maxima 6cyl that intermittly stops running while idling and in gear. Mostly this occurs at a trafic light or stop sign. It now shows no codes for any issues. This mostly happens once it is been driven 20 miles with no issues then it starts. The one time it would crank over just not start all other times it starts right up and goes till you slow down again.
I have replaced: MAF, IAP, knock sensor, computer, PCV, and fuel filter.
All the plug were replaced 6 months ago and still look great.
I have taken it to a dealership and another mechanic who tells me they can not find anything wrong. Of course they don't take it out long either.

It could be the fuel pump slowly going out. might want to check that.

What kind of maf is it. OEM or aftermarket. It must be oem or it will not work. It must be a Nissan maf.

We have the OEM MAF

How can I tell if the fuel pump is going bad. I have sunk so much money into this car.....

Test your fuel pressure first with a guage. Does your car crank a lot when trying to start it if not it is not the fuel pump then and these fuel pumps rarely ever go bad.

First I would put back your original ecu that came with the car because it seems it was not bad and plus that is designed d pacifically for your car and the 4th gen ecu don't ever go bad. Put that ecu back in and see if it helps much. You can also test camshaft position sensor to see if that is bad. If its Hitachi it should ohm out to 1600 to 2000 and a Mitsubishi is 2000 or above. That sensor will also cause the car to stall because that's our distrubutor.

How about the coolant temp sensor? Non-oem maf's are fine by the way - they just don't last as long. I'm on my 2nd $50 replacement maf. The 1st replacement one lasted two years.

No codes? The last time my car acted like that a code for the idle air control valve was thrown. I bought a new one only to find my orig was still good just was not snugged on tight by my mechanic when he did my power steering lines. So I'll probably sell my iacv sometime since I took it apart and cleaned it already.

If the coolant temperature sensor is bad u will have a high idle and the fans will stay on plus your car will run really rich. I had the same problem you described above Kswan 149 with my 97 quest van. I had replaced fuel filter and fuel pump and it turned out to be bad exhaust valves and three of my cylinders had low compression and 1 had zero and it was still running fine but it would stall at idle at the stop lights. Make sure u have compression in your engine as well.

Clean your iac.

The IAC was cleaned and had showed up in codes until I replaced with a new one.

I had intermittent stalling with no codes and no other issues and I was able to associate mine with 10% ethanol fuel. Most gas stations nowadays only sell it this way. If you can find it, try 100% gas or an additive from the parts store that will counter the ethanol.

Also, make sure to use 91 octane or better. I had stalling even with 91 octane and 10% ethanol. Switched to 100% 91 octane and haven't had any issues since.

What brand of plugs? I had an intermittent RPM dip at idle, although it never stalled out. Replaced my plugs (which looked fine) with NGKs and it went away.