a/c rpm problem - United Bimmer Community

**Exilion** · 03-04-2007, 05:10 PM

Hello everyone. Ok this is a problem I've avoided because I was busy and I didn't need to use the a/c in the winter. But now it's turning to spring and getting hot again. It's probably simple to diagnose but I wanted some outside advice as to what it was and how difficult it is to fix.

The problem is whenever I turn the a/c on the engine's rpm accelerates from idle to around 2000-2500 rpms. This obviously is not noticeable while the car is in gear but coming from a stop it can be annoying. All I can guess so far is that the idle control can't handle the strain of the a/c.

So... what do you think?

**c1apton** · 03-04-2007, 06:14 PM

Normally when you turn on the AC the idle should go up to compensate for the AC load but not to 2000 to 2500 -that's not normal. It should only go up a couple hundred rpms. Do you own a Bentley manual? You need to check the specs for high idle settings

**Exilion** · 03-04-2007, 08:29 PM

Unfortunately no and I lost my Hanes manual... I'll have to pick a new one up before I start again. I was doing pretty good using bimmerdiy.com

**Bibolt** · 05-21-2007, 06:51 PM

try replacing fuel pressure regulator, and try adjusting throttle position with the screw over the gas pedal wire, that worked for me,
even though my mech told me it had nothing to do with the fuel pressure regulator, it worked for me.

**elsabor67** · 05-22-2007, 12:11 PM

I am still troubleshooting mine because it does the same identical thing. If I figure it out before you do, I will let you know what I did to resolve it. If you get it before I do, could you pass me a PM and let me know what you did? Good luck.

**John L. Harrell** · 09-01-2007, 02:34 PM

I guess you have not resolved the idle problem?
A few things to check.
Is the compressor clutch engaging and is there a load, charged a/c system?
Is the throttle switch working/ properly adjusted?
What ECU is installed. ECU's prior to the 173 run 1.1 firmware which exhibits a jerkiness when the throttle is closed and compressor disengages. Swap ECU's to another of the same series or higher - 351,380,525,526.

Best thing for that Haynes manual is for it to be lost.
Do not dick with the idle mixture set screw or fuel pressure. You will screw up what is right. The ECU will be working overtime to compensate for what you are dicking with.
There is no idle speed adjustment for A/C operation. You are not working on a 68 Chevy!

Happy hunting.

**Exilion** · 09-08-2007, 12:25 PM

Wow sorry guys I must have spaced out for a few months there. Thanks for the info though. It seems alot of people are having this problem now

Oh yeah about the haynes manual...... I got a bentley manual and like I'm majoring in marine systems engineering. Hopefully I won't have many problems in the future.