Engine dying on slow down

[GhostTX]

Ok, so I replaced my battery this afternoon at lunch.
Went from a Motorcraft BXT 40R and bought a Super Start from O'Reilly:

http://www.oreillyauto.com/site/c/detail/SSB0/40R72.oap?year=2005&make=Ford&model=Mustang&vi=1431310&ck=Search_C0423_1431310_-1&pt=C0423&ppt=C0005

Now, this morning when the car konked out, I removed the battery so I could go buy a new one at lunch. So my car had no battery in it for 4 hours or so.

So after I replaced the battery, doing some in town driving, when I would slow to a stop, the idle would dip down below 500rpm and the engine would die. I have minor mods, Granatelli Cast CAI, and Flowmaster 17410. I've never had this issue before at all (2005 GT, 62K miles). One time, after the engine died, I would turn the key and the car wouldn't restart immediately. A/C was blowing, radio was on, but the engine wouldn't turn over for good 30+ seconds.

Did having power out for so long reset the computers to some default and the engine has to relearn? Any other idea? Is the new battery affecting this somehow?

[juiceweezl]

So I'm confused. Typically if those cars won't stay running at idle, the IAC is the primary culprit. Let's start over.

1) Is the car running fine under throttle?
2) Is it just not turning over with the new battery?
3) If yes, do you have stuff turned off (like A/C, lights, radio, etc.)?
4) Did you clean all terminals and make good connections with the new battery?
5) Have you tested the alternator? It could possibly be going bad and putting a heavy draw on the crank causing it to stall.
6) Is your theft light flashing rapidly when you turn the key on?

Answer those and we'll see if we can help you.

[camarenar]

In my 99 I had the same issue twice and both times it was the IAC.

[JC316]

IAC is the most likely culprit, but check your battery/alternator connections just in case. I forgot to plug the voltage regulator back in once and got symptoms like you are describing.

[GhostTX]

I did ensure the terminals were clean before I installed the new battery. In fact, bought terminal cleaner and scrubbed them up before install. I drove with "stuff" on and off. Didn't and still haven't checked the alternator, but all my idiot gauges don't indicate that.

So...I guess it's kinda related to the IAC. On another board, people recommended just a cleaning of the TB saying they had similar issues.

I went to a store and said I wanted TB cleaner, the guy got me carb cleaner. I stayed emphatic about the TB cleaner and we finally got me a bottle of CRC TB cleaner.

I found this nugget doing a search:


So, took off the TB, cleaned it up, put it back on, drove my normal commute and ZERO issues!

Amazing something so "minor" has such a huge impact.

[juiceweezl]

Glad it's fixed, but I bet it was the IAC. It's in the same area, so you probably got some cleaner in it and straightened it out. Nice job fixing it!

[astang95]

on an 05 GT. the IAC is combined with the Electronic throttle body, you can no longer replace just the IAC, its the whole throttle body!

[juiceweezl]

on an 05 GT. the IAC is combined with the Electronic throttle body, you can no longer replace just the IAC, its the whole throttle body!

Rarely does anyone actually replace the IAC on the previous gen models -- they just clean it.

[turbos66coupe]

I always replace them. I have seen the pintel rods wear a grove and cause them to stick, cleaning can't fix that. But general cleaning does help for awhile