CLK 500 Engine Idle
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From: 2000 ft over the FL coast in a B-17
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CLK 500 Engine Idle
I've recently noticed the idle on my CLK 500 varies with the AC on. When at full operating temp, in gear, with AC on its either 700 or 500 and varies every other traffic light or so. When it is at 700 if I turn the AC off it drops to 500 but if I switch the AC back on it stays at 500, if I rev the engine or drive a few more miles it will be back up to 700; shouldn't it go back up on its own while stopped or without reving?
I know the idle raises and lowers when the compressor kicks in with some older cars but I never noticed it in the CLK before as I always thought it stayed at a constant rpm when the AC was on.
I recently had the ECU changed due to the engine cooling fan staying on high speed so I'd really like to know if my car is behaving like other's here.
Please post your observations.
Thanks
I know the idle raises and lowers when the compressor kicks in with some older cars but I never noticed it in the CLK before as I always thought it stayed at a constant rpm when the AC was on.
I recently had the ECU changed due to the engine cooling fan staying on high speed so I'd really like to know if my car is behaving like other's here.
Please post your observations.
Thanks
Last edited by RJC; Aug 11, 2004 at 09:16 PM.
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Wow! The ressponse has been overwhelming, thanks to everyone for providing the feedback I needed 
I always try to help out other forum members when I can 
I always try to help out other forum members when I can
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Thanks for the reply. I'm curious to see how other cars idles are with A/C on in gear and at a stop; 450 rpms 650rpms etc. and does it vary? This info will be valuable when I visit the service dept on Tues.
Thanks
Thanks
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LOL RJC, I probably think its ok. You could bring it up to your dealership if it wasn't doing that before the new ECU but my guess is that the compressor was engaged as you were slowing down which made the idle up at 700. If you turn on and off the A/C at a stop the compressor might not kick on right away.
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From: 2000 ft over the FL coast in a B-17
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Originally Posted by AznxKCBoy
ok ill be going out tonite, after i drive it in a bit..ill put my car idle and then turn AC on and see if there is a difference. I'll post after! 
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From: 2000 ft over the FL coast in a B-17
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Originally Posted by AlBoston
LOL RJC, I probably think its ok. You could bring it up to your dealership if it wasn't doing that before the new ECU but my guess is that the compressor was engaged as you were slowing down which made the idle up at 700. If you turn on and off the A/C at a stop the compressor might not kick on right away.
The other thing that made it obvious was it would be at 700 with the AC on and if I hit the econ button it would drop to 400 but when I turned on the compressor even after waiting a while it never went back up again until I reved the engine...something's not right
One thing fixed and they screwed up something else; ahh the pleasures of visiting the service dept.
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Originally Posted by RJC
Hey Al. I wish what you were saying was all there was to it but since the ECU was changed my car idles normally about %75 of the time and the other %25 lower at around 400-450. I'm almost certain the car never did this before and that's why I need the feedback.
The other thing that made it obvious was it would be at 700 with the AC on and if I hit the econ button it would drop to 400 but when I turned on the compressor even after waiting a while it never went back up again until I reved the engine...something's not right
One thing fixed and they screwed up something else; ahh the pleasures of visiting the service dept.
The other thing that made it obvious was it would be at 700 with the AC on and if I hit the econ button it would drop to 400 but when I turned on the compressor even after waiting a while it never went back up again until I reved the engine...something's not right
One thing fixed and they screwed up something else; ahh the pleasures of visiting the service dept.
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From: 2000 ft over the FL coast in a B-17
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Thanks Al.
Well on the way to the office the car almost died at the first traffic light, it stuttered and stumbled then cleared but unfortunately no malfunction light. I asked a colleuge that drives on 03 500 to check his car out at lunch and he said his idle when warm is always at 650/700 with or without the AC on or off.
Lets see what the good MB doctor says tomorrow; now I've got to protect the stone interior in case the grease gremlins strike.
Well on the way to the office the car almost died at the first traffic light, it stuttered and stumbled then cleared but unfortunately no malfunction light. I asked a colleuge that drives on 03 500 to check his car out at lunch and he said his idle when warm is always at 650/700 with or without the AC on or off.
Lets see what the good MB doctor says tomorrow; now I've got to protect the stone interior in case the grease gremlins strike.
Last edited by RJC; Aug 16, 2004 at 08:17 PM.
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Thanks. That's what I thought; it shouldn't change.
Well I got it back today from the dealer and they raised the rpm up by 40 and it seems to be much better now. The car idles at +/-700 in gear with AC on and say +/-690 with AC off. The Tech said that they installed an 05 ECU last time I was in and it has slightly different settings than the 03 and 04's. I don't know if that's BS or not but they offered for me to do a side by side comp. I think my idle was too low after they put in the new ECU and the computer sensed it most times and brought it back up most of the time, so maybe they extra 40 rpm was just enough to keep it out of the danger zone. There were no codes from the car stumbling the other morning and I'm glad it's better now.
I saw a new 05 500 coupe and I/m not too sure about the new rim design again??? The center stack is nicer for sure as is the stock 55 deck spoiler.
There was also a red 05 55 CLK and the split spoke 18"s really helps the looks of the car, the new giant brake calipers and quad exhaust are to die for but the sticker was $78K... that's the base price of the new 997 Carrera S!!! I think I'd rather have a base 2005 S, what do you guys think?
Well I got it back today from the dealer and they raised the rpm up by 40 and it seems to be much better now. The car idles at +/-700 in gear with AC on and say +/-690 with AC off. The Tech said that they installed an 05 ECU last time I was in and it has slightly different settings than the 03 and 04's. I don't know if that's BS or not but they offered for me to do a side by side comp. I think my idle was too low after they put in the new ECU and the computer sensed it most times and brought it back up most of the time, so maybe they extra 40 rpm was just enough to keep it out of the danger zone. There were no codes from the car stumbling the other morning and I'm glad it's better now.
I saw a new 05 500 coupe and I/m not too sure about the new rim design again??? The center stack is nicer for sure as is the stock 55 deck spoiler.
There was also a red 05 55 CLK and the split spoke 18"s really helps the looks of the car, the new giant brake calipers and quad exhaust are to die for but the sticker was $78K... that's the base price of the new 997 Carrera S!!! I think I'd rather have a base 2005 S, what do you guys think?
Last edited by RJC; Aug 17, 2004 at 09:01 PM.
