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  #1  
Old 28-07-2014, 06:52 PM
alanw89 alanw89 is offline
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Default Air-Con and Idle

It seems that my air con hasn't had any gas in the air con for the last couple of years (was never that much of a problem in Scotland). But since getting it recharged last week I seem to have a terrible idle when its running. I'm sure I've read somewhere that the cars will idle a little higher than normal with it on but mine seems to hunt between 500 and 1300 at times. It will settle back to normal pretty much as soon as you turn the air con off.

Before getting the air con charged it had been idling high when first pulling away in the morning but a blip of the throttle would always sort it out. At times in stop start traffic it might start idling high but with the air con on it now seems to be noticeably worse and jerky on and off the throttle.

My question is would I be right in thinking that the most likely cause of this is going to be vacumn hoses/ Idle control valve? I think I've got most of the hoses back home, will need to check next week, but I'm planning on changing them all over and giving the idle control valve a good clean.

Is there anything else worth doing while the intake and everything is removed or am I barking up the wrong tree with regards to my dodgy idle?
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Old 28-07-2014, 09:38 PM
Imolacoupe22 Imolacoupe22 is offline
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I will be interested in this thread as I have the exact symptoms since my re-gas.
Although my aircon didn't work because apparently the compressor clutch has failed, could this be straining the belt/pulleys/idle?

Does your aircon work now?
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Old 29-07-2014, 06:02 AM
JuhaV JuhaV is offline
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Same symptoms here : idle without AC steady 700 rpm except right after a cold start elevated to 1200-1300 for a few minutes after which returns to normal idle (for accelerated heating up of catalyzers I suppose). When AC turned on, then idle is slightly elevated (about 900 rpm) an when the compressor switches on and off, the idle may take a slight down or upswing of a few seconds before becoming steady again.

However these symptoms have been reducing over the years when supposedly the pressure in the AC system has gone down. Right after the fill up they were much more noticeable and even distrubing. My car seemed to have some issues when the service was filling up the AC system. They had to do it 2 times before they were satisfied on the amount of gas they were able to drive in. I got the impression that the grams of the refrigerant specified for the car was rather high and the mechanic was not capable in the end to fill it up to that spec (S50).

All the time the AC has been otherwise providing nice cool air and the last fill up was summer 2012. Still going strong now during the heatwave and + 30 C temperatures.

Have others had problems reported by the mechanics when the AC has been filled up with new refrigerant ? For me, they had to force the service machining manually to do the phases, it did not go wright when they tried to do it automatically.

- JuhaV
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Last edited by JuhaV; 29-07-2014 at 09:50 AM. Reason: Fixed some typos
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Old 29-07-2014, 11:18 AM
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c_w c_w is offline
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I would have expected idle to be better on a good fill of gas since the aircon doesn't have to work so hard.

Mine on cold start idles at maybe 950rpm (1200-1300rpm sounds quite high) before coming down to 750ish. With a/c one it's raised maybe 100rpm and steady (you can feel assistance to throttle at slow speed, a bit like a choke, where the car drives itself very slightly).

I would guess the idle control valve might be a cuplrit, this should be able to maintain a steady and smooth idle whatever load or surprise the engine has near idle. Throttle switch may also caused some issues.

Last edited by c_w; 29-07-2014 at 11:30 AM.
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Old 29-07-2014, 12:58 PM
JuhaV JuhaV is offline
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Quote:
Originally Posted by c_w View Post
I would have expected idle to be better on a good fill of gas since the aircon doesn't have to work so hard.
It is the opposite : If you do not have the refrigerant in the system, the compressor will turn without much resistance. Only when you have the gas you will raise the pressure and the compressor needs to do some work and it will be pulling some power.

Forget to mention that I have a highly modified ECU with base program from M3. After switching into this, the idle when cold increased. Before that it might have been a bit below 1000 rpm.

Idle control valve has been cleaned recently and should work ok.

- JuhaV
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Old 29-07-2014, 04:50 PM
alanw89 alanw89 is offline
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As far as I can tell there must be some sort of low pressure cut out which stops the compressor clutch being engaged, as when mine was recharged it started squealing like mad every time the clutch engaged for the compressor. Figured the noise is due to all the crap and dirt that will be on the plates as they've been apart for at least a couple of years, it doesn't happen much at all now that its being used and cleaned itself up a bit.

With the high idle it will start in the morning around 1k rpm and and gradually come down over a couple of minutes, perfectly normal. But if I pull away and then stop again it will idle around 1500, small blip of the throttle and it will climb to about 2500 then settle back to normal and is usually fine from then on.

Will try and get a video of it at some point as seems its pretty common and then another one when its acting up with the air con on.

Quote:
Originally Posted by Imolacoupe22 View Post

Does your aircon work now?
Got down to 7.5 degrees from the vents, its lovely

Quote:
Originally Posted by JuhaV View Post

Have others had problems reported by the mechanics when the AC has been filled up with new refrigerant ? For me, they had to force the service machining manually to do the phases, it did not go wright when they tried to do it automatically.

- JuhaV
No problems with the actual charging on mine.

Quote:
Originally Posted by c_w View Post
I would have expected idle to be better on a good fill of gas since the aircon doesn't have to work so hard.

Mine on cold start idles at maybe 950rpm (1200-1300rpm sounds quite high) before coming down to 750ish. With a/c one it's raised maybe 100rpm and steady (you can feel assistance to throttle at slow speed, a bit like a choke, where the car drives itself very slightly).

I would guess the idle control valve might be a cuplrit, this should be able to maintain a steady and smooth idle whatever load or surprise the engine has near idle. Throttle switch may also caused some issues.
The hunting when the compressor kicks in suggested idle control valve to me, just seems like it can't meter the right amount of air in to keep things steady.
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Old 31-07-2014, 06:20 PM
alanw89 alanw89 is offline
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Ok got some videos today.

First one is a cold start this morning.
https://www.youtube.com/watch?v=M3CFMagiTWQ

Starts off fine (maybe a little high) and quickly settles down. Then I lift the clutch and pull away then dip the clutch and stop again, now idling at 1700ish. The two little blips are e but the very last bit of the rise is the car on its own before it settles back to 1k. Its usually fine from now on apart from very rarely when in stop start traffic and when the car is warm. This is Air con off.

Second is the car warm, at idle and switching the air con on.
https://www.youtube.com/watch?v=cqzCVgWmICY

Little rise at 3 seconds is me putting air con on. then nothing happens for a bit but on rolling forward on the clutch about three feet and stopping the idle hunts a few times and then settles, if I switch air con off in the middle of this it will normally settle straight away. If in traffic when warm it will do this about 50% of the time.

Is this the same as others are getting?

Im sure my clutch doesn't sound that squeaky in real life
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Old 31-07-2014, 08:01 PM
JuhaV JuhaV is offline
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Not the same. Your symptoms seem much more severe than mine.
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  #9  
Old 31-07-2014, 08:50 PM
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c_w c_w is offline
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I recall my car having a "bouncy" idle on a hot restart and needing to settle down. I'm pretty sure a new throttle switch fixed this. Worth a try anyway as they do wear at low throttle positions.
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Old 02-08-2014, 02:41 PM
kwoffa kwoffa is offline
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This may sound a bit Random..but when was the last throttle cable replacement? or oiled ? i have none of your symptoms but i did have my aircon pump replaced...as the clutch was/did burn out which made me replace the belt aswell..big black smoke from the rear of my car when i pressed the ac switch....instantly gone when ac turned off !
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