i have a 1998 mustang GT, but last year i swapped it for 03 motor GT, I am just curious what should my normal idle be at... I dont have my accurate reading because i think my tach is off because a long time ago when i did white face gauges i had to remove the needles so it may be off by some...right now it reads at like 500rpm...



the reason i ask is because no less than 10months ago i got a brand new battery and brand new aftermarket alternator. well just recently my battery light was coming on and off....it would come on and go away for days...then it came back more often and past couple days if i floor it and jack the rpms up the light go's away and stay off for a little bit ....but now i start the car and the damn battery light is on, even while regular driving and i punch it and give it gas and it turns off but instantly comes back on..

I am going to get the alt/battery checked today just to rule it out, but i dunno how it could be bad,its practically brand new..

I was talking with a mechanic and he said i could be idling to low.... so any thoughts and ideas would be great!

 

From what i understand normal idle should be around 750-900 rpm. Mine is at 850.

 

650 is what my truck and car idle at.

My car ****ing pisses me off though. I have been chasing an idle issue for about a year now. My car will run fine for about a month, then decide it wants to idle at 1200. I have not found anything in the tune that shows why it would do this. its like the PCM is having a ****in heroin bench and tweaking.

 

It depends on the stock tune, we had this discussion over at Modded Mustangs a month or so ago, here are the various idle settings I found in a few spot-checked stock tunes:

• 736 in RYAF1.XSH2 (my '03 GT);
• 680 in RYAF1.MDE3;
• 640 in RYBE2.YDH1;
• 800 in FBLF1.VDX1;
• 720 in RVAFA.NUX2;
• 625 in FMAG0.RMR0;
• 640 in RZAO1,BMD0;
• 736 in FBFG2.RKN2;
• 705 in RVAF1.KSG0;
• 680 in CRAJ0.AOL3;

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My car idles fine around 650 till i turn the A/C on or the defrosters, then it bounces like a bitch and i hate it.

 

Mine used to do that, but I added the appropriate values in the tune to fix that. I just cant seem to track down the idle issue. I have no idea what would cause a car to just slowly rise up to 1200 and stay there. Its retarded. It only does it like once a month. I have to disconnect the battery and reset the KAM.

My TB settings are correct so I dunno WTF it is.

 

A sticky/failing IAC would do that...

 

What did you change in the tune? There's a whole bunch of interaction between the various IAC "dashpot" settings--have you tried returning them to stock and then adding them in one at a time?

 

Yes. I havnt touched anything in the tune other than the A/C. Iv played around with a lot of stuff, but no matter what I do it works for a while, then same ol same ol. Iv replaced the IAC, there are no vacuum issues, nothing like that.


I think I may just have a bad computer or something. Theres no rhyme or reason why it should do it over time you know. A code is a code is a code. As far as I understand the KAM is not an adaptive learning system as you have to reset it after certain mods.....so I cant see why its doing this over time.

 

its funny because i always thought something with my IAC was goofy. When im going to a stop the idle will come down real slow the just go *plop* right back to idle real quick.