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Matt
Matt, Mechanical Engineer
Category: Car
Satisfied Customers: 23086
Experience:  BEng hons Mech engineering, in auto industry 22 years
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If have a new Renault Clio my 4, when i change from 1st to

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If have a new Renault Clio my 4, when i change from 1st to 2nd gear the revs hold its between 2000 and 3500 rpm then a few seconds later it drops,
Some times its ok and it starts to do it when the cold light goes of

Hello

I'd say the 1st thing to check is the state of the clutch position switch

this is located on the top of the clutch pedal in the drivers footwell

as its a simple 2 wire device its easily tested with a multimeter to confirm its switching on and off with the pedal

its used by the ECU to switch into a different strategy for gearshifts

so if its not switching this can create the issue you describe

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Thanks Matt

Customer: replied 1 month ago.
I cant work out why it dont do it at 4000 rpm or 2 to 3, 3 to 4 ect

well usually the gearshift strategy is gear specific, as each gear has a different inertia and there's different adjustments for each

and they tend to be strongest in the lower gears

try testing the switch and examining its wiring for any damage or signs of crushing / abrasion

Matt and other Car Specialists are ready to help you
Customer: replied 1 month ago.
Well today i was slowing down to a junction going down hill, went in to 1st gear at a very low speed let the clutch up and it shot forward in to the junction

OK

1st check the clutch switch and then if thats OK then

This could be an airleak after the airflow meter, any air dragged in here isn't 'seen' by the ECU and so not compensated for and can lean the engine out and can also allow the engine to rev up when not desired causing rough running and a high idle
As its a mechanical fault it tends not to turn on the fault light and you can sometimes hear a 'hissing' noise with the engine running.

Check the hose clips for tightness and inspect the trunking for any cracks or splits and also all the vacuum system, the small bore pipes and fittings for cracks and missing parts.

The best way to locate a leak is to have the engine running and warm and then spray lighter gas /propane or brake cleaner around each joint in turn. If the engine rev's up you've found your leak.
Now you might think that spraying lighter gas around a hot engine isn’t wise, however the flash /ignition point of gas is about 400°C so you need a naked flame or spark to set it off and I’ve used this method for many years without incident.
Work your way through each possible joint one at a time and you should find it. I use a slightly flattened piece of brake pipe and some rubber hose from the can of lighter gas to provide a spraying 'wand' and allow a direct blast of gas into each area, especially those difficult to reach with large implements.

Air leaks are very temperature dependent as gaps can open up as things expand with temperature so depending on how the leak occurs ( on a hose joint with a clamp expansion will help seal and on a vacuum hose expansion will make a leak worse) so leaks can be better or 1 vacuum leak path that you won't find with the above test is if the brake servo is leaking
so try clamping off servo hose to see if this has any effect

Customer: replied 1 month ago.
Ok thank you
Customer: replied 30 days ago.
Hi Matt
Thank you for the information to try on my car, but the dealership was not interested in the information as Renault UK technical say that it is a characteristic or the car and is to allow for a smooth gear change.
Now the car is still holding the RPM but is now increasing before coming back down so i think the engine is running too lean.....Thanks

Hello

I'd try a small independent garage whom will be more likely to listen and investigate

doesn't have to be a Renault specialist as what I'm suggesting can be tested by any competent mechanic