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Matt
Matt, Mechanical Engineer
Category: Renault
Satisfied Customers: 21727
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I have a renault Laguna 2.0 dynamic 150 bhp - bought the car

Customer Question

I have a renault Laguna 2.0 dynamic 150 bhp - bought the car at 53000 and it has has rough idle since, worse when the aircon is on, however not constant - some days it doesn't at al some days it does, the car does not stall. I have changed the fuel filter, serviced, put a K&N long life air filter and several doses of injector cleaner but the problem does not go away?
Submitted: 1 year ago.
Category: Renault
Customer: replied 1 year ago.
the car now has 85000 miles remaining with the same issue, not better or worse
Customer: replied 1 year ago.
Where is my answer please I paid £31 for a quick response but we are now well over a day
Expert:  Shantal-Mod replied 1 year ago.
Hello,
I'm Shantal and I'm a moderator for this topic.
I've been working hard to find a Professional to assist you with your question, but sometimes finding the right Professional can take a little longer than expected.
I was checking to see if you had already found your answer or if you still need assistance from one of the Professionals.
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Shantal
Customer: replied 1 year ago.
I need an answer please so happy to wait
Expert:  Matt replied 1 year ago.

Hello

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.

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 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 flattenedpiece 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.

It’s also worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a poorly pump will all result in insufficient fuel being delivered to the engine

Might also be worth checking the wiring and connector to the airflow meter for any signs of corrosion or damage. you can do a quick fault find if you unplug the meter and run the engine without it.

if the engine condition is the same then chances are the meter or the connection to it is faulty

Air leaks are very temperature dependent as gaps can open or close up as things expand with heat, so the weather and engine temperature can effect them.

This leads them to be quite intermittent in the case of mild leaks

its also worth cleaning the airflow meter by removing it from the car and spraying the exposed sensor wires inside the tube with a brake or switch cleaner - ensure that the cleaner is one of the old fashioned, non Eco type that does not leave a residue

On no account touch the sensor wires with anything physical as they are extremely fragile

Expert:  Matt replied 1 year ago.

Hi

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