'98 GT 4.6 2V - 95k miles. For about 2 months it has been shutting off right after it started up, my '69 would do it every so often and thought nothing of it thinking the starter just didn't fully engage. Well a week ago it wouldn't start or turn over at all just a single click that I thought was the starter, tested it and everything came out right. Replaced it anyways cuz it's got a lot of short trip starts on it. Still single click that sound like it's coming from the transmission now, or did before but couldn't tell from listening inside the car with no helper. These electronic vehicles with all the sensors and relays really make me mad, I could go for days on the subject but will take any advise on this one for now.

 

How old is the battery? "a lot of short trips" means the battery is mostly likely not getting fully charged after each startup. That could address the "click' you are getting right now. Have the battery load tested, a simple voltage check won't tell you much if a cell is bad.

As for the shutting down right after starting, check your throttle body butterfly and Idle air control valve for buildup/dirt. If those are gummed up, it may have a hard time starting first thing on any given day. ECU is in open loop mode so it runs on predetermined fuel maps for 30-60 seconds before it goes closed loop and starts taking sensor readings to adjust idle etc. Again, a lot of short trips over time contribute to that.

 

1. The battery is no more than 2yrs, I live in Seattle so freezing has not been a problem and I dropped my friends battery in out of his '97 and same thing. I clean the IAC about every six months or when it starts with the subtle stutter. A friend told me to test the Neutral safety switch but not sure how to go about that, I'm not to good with electrical diagnostics. I do have a multimeter but have mostly used it to make sure power is present when it should be. My car is weird with most of the parts not in locations of Mustangs of same year and most manuals and video tips are useless until I finally track down a part location so not even sure if the specs. listed are correct.
2. I appreciate the quick response with it being the Holidays and all. I'm this close to selling it but i bought it from my sister after she found out that child carseats don't fit in the back seat, and she passed away a couple years ago and want to keep it and restore it for her grandson to drive in a couple years.