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Discussion Starter #1
Hi all,

I am a noob at this forum and not experienced with cars either, not injected ones anyway.

Ok, my query. I have a '96 1.8 8valve Laguna. It idles at between 1200 and 1500 rpm. You can see the idle speed valve hovering above the throttle stop (correct terminology?). There is no other problem and it runs ok.

I have been told it will not pass it's next MOT like this as it is not possible to get the revs low enough to test the emissions.

Any help is appreciated.
 

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Hi and welcome to the forum iam sure it will be able to come down but i cant help but iam sure someone will help you soon all the best Donald
 

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Hi Fraser,

Thanks for your input. It makes sense. Someone suggetsed I check for air leaks which I have done and cannot find any so I am turning my attention to the MAF sensor as you suggest.

Unforunately I can find no mention of it, or the pipe, in the Haynes and my local dealer is having trouble finding it too :confused: . Where on the engine are these and is it possible to test the sensor?
 

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Discussion Starter #7 (Edited)
I did wonder about the idle speed control valve but it can be seen moving and changing the revs so it seems to be working ok.

Thanks for the input.

Visited another renault dealer today who said that there's so many sensors etc that I would have to take the car in and get it checked over. 1 hour's diagnosis would cost £93!!!

Can someone please explain where the MAF sensor is located. There is no mention of it in the Haynes.
 

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Hi Boozer - can you see the idle control valve moving back and forth - if so it shouldn't be it should remain quite steady with only minor changes - i sugest you take it off and clean it - just to be sure:) Not sure about your model but the later Laguna have a MAP sensor on the inlet manifold.
 

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Discussion Starter #10 (Edited)
Finally got round to spending some time on the old girl - not my main transport, see.

....can you see the idle control valve moving back and forth....i sugest you take it off and clean it - just to be sure:)
The idle speed control valve does indeed move back and forth slightly. Here's what I have done:

Fitted a MAP sensor from a Fiat Punto - it is an MS002 sensor and it fits so I thought I'd try.

Removed and cleaned the idle speed control valve - it wasn't dirty but followed your advice, Noel and Ross:) .

Cleaned all electrical connections to and from injector assembly.

Checked continuity between all the injection components as best I could and found nothing wrong, as far as I can tell.

Guess what........No change!!! The idle speed control valve still moves and the revs still 'hunt' between 1200 and 1600 :confused: .

Something must be telling the idle speed control valve to misbehave.

Any more ideas out there please :( .
 

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A mate has had similar issues as this which were helped by: new air filter and error code reset, and unltimately fixed by: new plugs! Go figure, don't understand it but the car is fine now, we were thinking MAF, idle valve, even the lambda sensor at one point - none of it changed anything except when we disconnected the MAF the revs could be lowered to stalling point and held by manually operating the throttle which took us down that route - the ecu error codes were stored up from the entire history of the car I think, none were relevant but things did improve when they were cleared. :)
 

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Discussion Starter #12
Nice one Schmooster. I am all excited now:p

I checked coolant temp sensor, knock sensor and as much of the wiring as I could, as well as what I described above. The next stage would be to look for an air leak in the injector body and/or hoses.

I have already fitted a new air filter and I promised myself that when (if) it is all sorted I will treat the old girl to new plugs!!!! Looks like she will get them sooner than I thought.

Will get some tomorrow and fit them when weather allows. Fingers crossed.
 

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Thanks to Schmooster for the advice. I fitted the plugs and it made the car run much smoother. It didn't cure the fast idling problem though :( .

Here's another thought:

The engine seems to be getting quite hot. The water pipes warm up quickly to the touch and the needle spends most of it's time in the upper quarter. I have checked the water temp sensor, which seems to be working ok. The needle moves in the usual way even with the sensor disconnected!!!

Also the car seems to use a lot of fuel yet the plugs are whitish, indicating a weak mixture. Is this all a clue?

Could something be telling the system it is cold when it is hot? Could this be causing the fast idling?

Will clearing the ECU memory, as suggested above, really help?

I am now leaning towards an air leak in the injector unit.

I am running out of ideas and don't want to scrap the car, neither do I want to throw horrendous amounts of money at Renault.

Any thoughts still very welcome, PLEASE.
 

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Lamda sensor? Not sure if this (via the ECU) controls the idle air control valve (or just the MAF controls it?), but this would explain the lean or rich mixture as that's what this sensor controls by monitoring O2 in the exhaust cycle.

Another friend of mine is having issues with hunting revs and rich mixture, he's fitting a lamda sensor this weekend, I'll let you know how he gets on.
 

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Discussion Starter #15
Interesting thought, Schmooster. I am sure we all remember the fiasco with Tesco petrol and lamda sensors. I always buy decent petrol but you never know. Just shows that Lamda sensors can be delicate.

I am interested to know how your mate gets on.
 

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Over the weekend I tried replacement knock sensor and MAP sensor. Also tried the other thing which is located just next to the front off-side shock mount (whatever it is). None of these things made a difference.

I have been told that if an engine is running extremely rich it can 'wash over' the plugs giving the impression it is running lean. I am steering even further towards the Lambda sensor.

The car is booked in to local garage for diagnosis (£32) on Thurs am. Fingers crossed.

How did your mate get on Schmooster?
 

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Hi Boozer, I'm not sure how much of this will apply to the Laguna as my experience of this is in relation to my Alfa, but I recently had this when I replaced the idle actuator on it (idle control motor). When I replaced it, the car idled at 5000rpm! Not too worried though, as I know these need to be reset on a computer, so I had it reset.

All was good until the car warmed up. After the fan cut in for the first time, the car would start hunting for idle from anything between 500 - 2000rpm.

I eventually replaced the the idle motor again with my old one and problem was sorted (i.e. the replacement idle motor was faulty).

In short, if it can be reset, have the idle valve reset. If not, I think thats where your fault may possibly lie.

One other thing, have you checked the piping from the MAP? I think it goes to the manifold.
 
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