Rough idle when air is on

ttopstang

Active Member

Sep 6, 2007

306

1

28

Birmingham, AL

Jul 27, 2010

#1

• Jul 27, 2010

• #1

The car idles fine util you turn the air on then it jumps up and down and will even go down so low to shut off some times. Car is bone stock 92lx 5 spd.

I adjusted the TPS to .98, and timing is at about 13*, but I havn't cleaned the IAC yet. I have never owned a mustang with air so I was wondering if theres another step I should take.

 

B

boxcarracer89

Member

Mar 26, 2009

153

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I live in Roswell NM

Jul 27, 2010

#2

• Jul 27, 2010

• #2

Ive got the exact same problem, but mine is extremly modded!

 

HISSIN50

"How long does it take to get help in here?

15 Year Member

Nov 29, 1999

31,179

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Jul 27, 2010

#3

• Jul 27, 2010

• #3

Any codes?

If the idle is ok at all other times (suggesting a vac leak is not the issue), the IAC is probably acting up. Sometimes they figure themselves out if your car just recently came out of hybernation, but since your car is stalling, cleaning or replacing it might be needed.

 

ttopstang

Active Member

Sep 6, 2007

306

1

28

Birmingham, AL

Jul 27, 2010

#4

• Jul 27, 2010

• #4

I don't think its a vacuum line, but I will check, and I will be cleaning the IAC. Idle is good all other times, only when A/C is on.

And the voltage jumps up and down ALOT as you rev it. I think its the alternator getting pissed at that electric fan.

 

jrichker

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Mar 10, 2000

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Dublin GA

Jul 27, 2010

#5

• Jul 27, 2010

• #5

See the "Surging Idle Checklist for help with all your idle/stall problems. Everything you need to find and fix idle problems is in there.

The first two posts contain all the updates to the fixes. At last count there were 24 possible causes and fixes for surging idle/stall problems. I continue to update it as more people post fixes or ask questions.

 

H

Haus

Member

Jul 20, 2005

408

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16

Jul 27, 2010

#6

• Jul 27, 2010

• #6

ttopstang said:

I don't think its a vacuum line, but I will check, and I will be cleaning the IAC. Idle is good all other times, only when A/C is on.

And the voltage jumps up and down ALOT as you rev it. I think its the alternator getting pissed at that electric fan.

Click to expand...

Did you upgrade from the stock Amp Alternator?

but anyway im interested in finding out your results. My car does the same, but i think my IAC is starting to go.

 

ttopstang

Active Member

Sep 6, 2007

306

1

28

Birmingham, AL

Jul 27, 2010

#7

• Jul 27, 2010

• #7

Stock alternator for now.

jrichker, I found your thread right after I posted and its very informative. I will try to keep yall updated but I probably won't be able to get to it until this weekend.