Please help me figure out what is going on with my idle.

[CalmLikeaBomb]

Originally Posted by mac10chap try turning and leaving your headlights on and unplugging the negative cable from your battery for 15 mintutes. This will completely drain all power that is used to keep PCM tunes loaded, etc. Put the cable back on and reload your tune. Also, I know that you can go through a brenspeed tune and reconfigure the settings. You didnt happen to do any of this did you??? Nope , didnt touch any of the tune settings. Slighty update: I went to my car and put the terminal back on the car and cranked it. RPMS shot up and leveled down , let the car temp gauge go the middle, then let the AC run for a minute or two. When I pulled out of the parking lot, I could instantly tell a difference in throttle response and torque down low. The idle problem is fixed with the AC turned off. I REV it up and it returns to the preset idle. However, I still notice a slight funky idle one time when coming to a stop with the AC on, then it returns to a normal idle. I hope it goes away with a little more driving.

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[CalmLikeaBomb]

Also I thought there is no need to reload the tune even after the battery reset since the tune is stored in a different part of the cars memory.

[05 Mustang]

Originally Posted by CalmLikeaBomb

Also I thought there is no need to reload the tune even after the battery reset since the tune is stored in a different part of the cars memory.

that is correct.

[CalmLikeaBomb]

Ok guys slight update. I cleaned the MAF sensor with maf sensor cleaner after resetting the ECU not too much change.


Here are some videos:

1-

When I initially start up the car the needle slams down , and I dont think Ive noticed this before. Is this normal?

http://www.youtube.com/watch?v=xdafV8QM-z8

2-

Here is the idle with the AC on, in the vid I shut it off and show how the idle jumps. When you notice the dip in RPM's I can feel the car studder for a second.

http://www.youtube.com/watch?v=Q32-FTYSvL0

Any other ideas? Let the car learn for another few days?

[CalmLikeaBomb]

anyone?

[Kotobuki]

I'm gonna say that second vid looks exactly like what my idle was doing with the alternator dying. Take it down to Autozone, or O'Rielly's or Murray's or whatever you have around you, and have them check the alternator. It should be free, and take all of 2 minutes.

IF there's a problem, it's going to be a bad diode. Find an Alternator shop in town, and take it to them to have it re-built. A replacement runs from about $250 to $400. I got mine rebuilt for less than $60 out the door, and it only took about an hour and a half.

[CalmLikeaBomb]

Damn im going out of town on a road trip this Friday through Sunday, do you think ill be okay?


The alternator seems like a route I havent checked, but how would that explain the initial startup rough idle in the beginning that almost sounds like a misfire?

[CalmLikeaBomb]

Could my battery just be going bad? I havent had to jump it yet though.

[CalmLikeaBomb]

Got my battery and alternator checked. Both checked out just fine and charging like normal.

[05 Mustang]

have you checked or changed your plugs recently? I've heard that bad plugs can cause idle problems..