Help - Fluctuating idle in C36
Thread Starter
Junior Member
Joined: Dec 2001
Posts: 36
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From: Philippines
95 C36 AMG, 02 SLK320, 06 Accord V6, 08 BMW 335i
Help - Fluctuating idle in C36
Gents, My 95 C36 suddenly developed a peculiar idle today. It fluctuates from 1000 to 1700 RPM in approx 1-second cycles, in gear or in neutral. This is scary because the car speeds up by itself when the RPM climbs and brakes can hardly hold it.
I shut the motor off but the problem was still there when I re-started. I shut it down once again and when I fired it up after a couple of seconds, the idle was now steady but very low (400-450 RPM). There are no check engine lights showing and everything else seems normal.
I did a search but can't find any posts with these particular symptoms. The plugs are about 1 year old (less than 15,000 km) and car is very smooth and powerful until today.
Assistance in troubleshooting this malady is highly appreciated.
I shut the motor off but the problem was still there when I re-started. I shut it down once again and when I fired it up after a couple of seconds, the idle was now steady but very low (400-450 RPM). There are no check engine lights showing and everything else seems normal.
I did a search but can't find any posts with these particular symptoms. The plugs are about 1 year old (less than 15,000 km) and car is very smooth and powerful until today.
Assistance in troubleshooting this malady is highly appreciated.
Senior Member
Joined: May 2003
Posts: 332
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From: LI, NY
02 W163, 84 W123, 03 E39, 98 E39
Changing Idle
Did you by chance just start using your A/C when this happened? I had a similar thing happen last year with a 96 C220. When it was very hot (over 90F) , and with the A/C on, the engine revs would pulsate about 500 rpm every 1-2 seconds.
What I finaly found out was the A/C compressor was cycling on/off every 1-2 sec and this was changing the engine revs. The reason the A/C was cycling, I found out, was that the A/C system was over-pressurized. All that needed to be done was remove some refrigerant to solve the problem.
What I finaly found out was the A/C compressor was cycling on/off every 1-2 sec and this was changing the engine revs. The reason the A/C was cycling, I found out, was that the A/C system was over-pressurized. All that needed to be done was remove some refrigerant to solve the problem.
