A friend got in her 03 mustang GT and when it started, it initially ran very rough, she turned it off, tried to start it twice, but it wouldnt start. It would turn over but just not catch.


She tried to start it again and it started, but all of the guages pegged to the right, then returned to normal. She drove the car and it ran fine. She popped the hood this afternoon and the battery had corrosion on it which she cleaned off.

She used the car today and it ran fine, tonight she started it (it runs smoothly) a couple of times and the guages pegged to the right and returned to normal postion 2 more times.

She bought it used in 04, and has never replaced the battery. Does anyone have any ideas what could cause this? thank you in advance.

Mike

 

The gauges are resetting because the KAM (Keep Alive Memory) is being cleared when the car is off, or while it's being cranked. This could be because of low battery voltage, corroded terminals, or a blown fuse (5A in location 21 of the fuse box under the dash).

I don't know at what voltage the KAM will clear, however cranking the engine with a weak battery and corroded terminals could do it...

 

Thank you Cliff.

Would that cause the engine to run rough as well upon start up, it only happened once so I think it is an isolated event.

 

It could, because the PCM would be running on default rather then learned parameters. You need to get the battery checked and terminals properly cleaned/replaced yo make sure things are right.

 

My GT was doing the same thing but with a low voltage effect that was making 1 headlight dimmer than the one. My problem turned out to be a short in the multi-function switch. Was replaced and has ran like a champ since then.