Help! Surge/lunge When Ac Is On

A

amanda0331

New Member

Jan 6, 2015

2

0

1

Jan 6, 2015

#1

• Jan 6, 2015

• #1

Ok so i'm going to describe this as best i can...
Whenever I am at a red light or any time my foot is on the brake and the car isn't moving. it will rev up/surge like it's going to lunge forward if i take my foot off the brake. This ONLY happens when the a/c is on. Nothing when it's off.
Any ideas????

 

Mattstang04

15 Year Member

Sep 15, 2006

1,152

144

104

St. Louis, MO

Jan 6, 2015

#2

• Jan 6, 2015

• #2

I have a manual and the engine will sometimes idle up while in neutral, when the a/c fan kicks on. Its a normal occurrence as best I can tell. The engine revs up via the idle air control to counteract the extra load of the a/c fan and compressor running.

 

wmburns

SN Certified Technician

Aug 14, 2009

5,892

514

204

Houston Texas

Jan 7, 2015

#3

• Jan 7, 2015

• #3

The PCM maintains two IAC idle trim values. AC on and AC off.

Here's my take. Your AC is low on Freon. This is making the AC short cycle. The motor isn't idling long enough to allow the PCM to re-learn new AC on idle trim values.

Try jumping the AC low pressure clutch cycling switch to force the AC to run solid for so 5 minutes with the motor hot.

Or fix the AC.

Does this help?

 

restomod66

Active Member

Apr 15, 2003

136

20

29

San Jose, CA

Jan 7, 2015

#4

• Jan 7, 2015

• #4

They will always surge just a bit with the AC running, this is common with other vehicle makes as well. However, mine got pretty bad and once I re-charged the AC the problem improved dramatically. I also think you're low on Freon.

 

A

amanda0331

New Member

Jan 6, 2015

2

0

1

Jan 13, 2015

#5

• Jan 13, 2015

• #5

thank you all! I will let you know if these help!