Renault Scenic - scenic high idle

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Tue 1 Mar 2016 14:55
Renault Scenic - scenic high idle - nicho1120

I wonder if anybody could assist. I have a 52 reg 1.4l scenic. It has recently been idling at between 1500 and 2000 revs. Car drives fine until it heats up a little and I come to a stop. It then starts to rev up and down between 500 and 2000 revs. Its as though its gasping for air. Checked all pipes for leaks. Changed coils and coolant sensor but no joy. Anybody any ideas or experience of this.

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Wed 9 Mar 2016 12:39
Renault Scenic - scenic high idle - glowplug

You really need to get it connected to a Clip diagnostic interface to see if there are any fault codes or strange parameters. Swapping parts could become expensive before you find the fault. And being a Renault it could be a faulty wire or connector. I've not worked on petrol Scenics but I believe the dephaser pulley on 16v engines causes various problems.

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Wed 9 Mar 2016 12:52
Renault Scenic - scenic high idle - slkfanboy

Idle issue could be a number of things including the O2 sensor, MAF or air leaks. This is really quite complex to diagnose and expensive to randomly change parts until it's solved.

Edited by slkfanboy on 09/03/2016 at 12:53

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Wed 9 Mar 2016 15:11
Renault Scenic - scenic high idle - Railroad.
The idle speed is controlled by a stepper motor which allows varying amounts of air to bypass the throttle. If your idle speed is erratic then it's likely that the idle speed stepper motor is all over the place. This could be due to carbon build up in the throttle body, or a worn or dirty throttle butterfly valve. Make sure the throttle stop is correctly adjusted, and that the throttle potentiometer is also correctly set. If your engine has an EGR system make sure the valve closes fully at idle. Anything wrong in these areas will mean the ECM will be continuously operating the ISTM to try to obtain the correct idle speed. Also make absolutely certain you have no intake vacuum leaks.

Ignition coils were never likely to be the cause unless the engine is misfiring.
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