stalling in idle & scanner cannot connect for codes

[3430willow]

Hello. I have a 2000 Nissan Maxima with 120,000 miles. A couple of weeks ago, as I was pulling out of work, my car died. It was over 100 out that day & it started right back up & was fine. Then, it did it a few days later when I was leaving work. Those are the only 2 times it has actually stalled while I was driving, but it has stalled several times now at stops. I had someone else drive it to see what they thought & it drove fine for them, but they did notice that the radio went off & only came back on after intentionally hitting a bump. I took off the MAF sensor & cleaned it because over the years I have had to do that once or twice a year to keep a smooth idle. This started out as an intermittent problem, but now is pretty consistent. I can usually keep it from stalling by giving it some gas in park at a light. Since cleaning the MAF didn't seem to help, I knew I had a problem & took it to a quick lube that has scanned for trouble codes for me before. He said it wouldn't connect & told me to try O'Reilly's. At O'Reilly's, it wouldn't connect & they said I should check the radio fuse. I had forgotten about the radio issue & sure enough, the radio was on, but the lights were all off & it looked dead. Anyway, I changed the fuse (didn't look blown) & the radio lit back up. I took it back to O'Reilly's & they said that only 4 of the 6 connections were being made & they couldn't read the codes. Any ideas why the OBD won't connect to the scanner? For the stalling problem, I am leaning towards IAC valve which hopefully hasn't ruined the ECU (how would I know?), possible O2 sensor or maybe the MAF needs replaced instead of cleaned. Since I have had the car, I have replaced the starter, brakes, all 6 coils & plugs, done a valve seal job. These I all did by myself even though I am for sure no mechanic, but with the help of forums, it was ok. I also had to have a new battery & alternator last year. My car has ran like a new car for the past year until this. I really want to get it going again, but don't just want to start guessing & throwing parts at it, but until I can figure out how to get it to connect to the scanner, I'm stuck....

[4ofclubs]

usually the scanner cant hook up because your cigarette lighter(or whatever you want to call it) fuse is blown.

[3430willow]

Ok. I will go check & replace that right now & see if that helps. Thanks.

[3430willow]

So, I checked the lighter fuse which looked fine, but replaced it & this time took it to Auto Zone for a scan & it connected. It gave me a P1320 code which would point towards coils, but I have replaced twice now with the last time being a year ago. I think because I didn't replace them with oem coils, the code just won't go away. I will still check each individual coil just to make sure, but it's not acting anything like my previous bad coil times. It is running & idling smoothly, just quietly dropping out while in idle Drive at stops. It is pretty intermittent. Today it has been doing ok. So, I don't really feel like the scan did me much good. So, maybe I should take it to a shop for a diagnosis? I'm fine with that, I just don't want them to charge me for what I got for free already & tell me I have coil probs. But, I don't want to start throwing hundreds of dollars in parts at it unless I know the actual problem. Does any of this scream out anything to anyone?
The IAC valve sounds probable since it's a problem on this car. I always think of it as being an erratic idle or a really high idle, wheras mine is low & then just bottoms out. If it is IAC, should I try cleaning it first or is that a big no no? Also, I don't want to fry my ECU. Would all my blown (but not visually burnt) fuses indicate I may have already damaged the ECU?
I cleaned the MAF sensor & that didn't help, plus in the past when it was dirty, the car was running sluggishly & a little rough until I cleaned it. Now, it's not. Could it be the cam position sensor? O2 sensors?
What do you feel like my next step in diagnosis should be?
Sorry if I am missing the obvious, but I am a woman that until I had this car had only ever put gas in... Now, I have changed coils, plugs, starter, valve seals (that was a rough one), etc, etc. When the garages quote me prices, I hit the internet & figure out how to do the repairs myself. I can on this, too, I just don't know how to diagnose. Sometimes, I want to give up on this car, but I have grown a bit attached & plus, the repairs are cheaper than a car payment. Any help or ideas appreciated.