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Author Topic: Unstable idle J117  (Read 14317 times)
Anders Dinsen
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« on: December 12, 2004, 07:46:31 am »

My J117 Espace from 1987 is suffering from unstable idle. Revs dip periodically, if I'm driving at low speed the engine may stop, and then it's impossible to start until it's become cold again (took me 20 minutes last week!)

I've fixed the problem by turning the idle screw on the throttle valve housing allowing enough air to pass outside the valve to keep the revs so high that they don't dip.

I've been looking for air leaks in the inlet manifold, with no success. I've been hearing a sound from there that could be an air leak, but is probably the noise the fuel pump is making in the fuel.

Could it be my lambda-sensor (oxygen sensor)?

I have a very bad engine electrical system and plan to replace the wirering (sensors seem okay), but I have checked it all through recently, and it seems to work.

Here's an image of my not-yet-pretty engine:



Cheers,

Anders
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'82 Murena 2.2 prep 142
'01 Grand Espace 24v
'08 Smart Fortwo 0,8 cdi
Anders Dinsen
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« Reply #1 on: December 12, 2004, 05:58:38 pm »

I'm quite certain now that what I've heard is the fuel pump making noise...
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'82 Murena 2.2 prep 142
'01 Grand Espace 24v
'08 Smart Fortwo 0,8 cdi
Anders Dinsen
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« Reply #2 on: December 14, 2004, 09:10:55 pm »

It's not the lambda sensor! This evening I connected an oscilloscope to the lambda sensor, and after the initial startup of the engine, the voltage starts switching between 0V and 0.62V with a period of a couple of seconds.

So the regulator loop, including the sensor works!

http://www.wps.com/LPG/o2sensor.html (very informative!)

Revs dip with the output voltage => lean mixture, dipping revs...
Why do revs dip with lean mixture?

I have no air leak, it was the pump I was hearing. So it's probably too little fuel... fuel pump.... it's very noisy, maybe too low fuel pressure...?

Next step is one of:

1. Try another fuel pump
2. Have the fuel pressure measured

Comments anyone???
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'82 Murena 2.2 prep 142
'01 Grand Espace 24v
'08 Smart Fortwo 0,8 cdi
Will Falconer
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« Reply #3 on: December 14, 2004, 09:45:05 pm »

Although it's good to investigate the problem yourself, have you had a check with a diagnostic computer?

It doesn't have to be the official Renault one, any garage with modern facilities should be able to plug your car in and give you some clues to finding the problem very quickly. The Espace on board computer stores every problem occurring until its been downloaded and cleared.

I recently had a problem with my 24v Espace, running like a Murena with a Solex carburettor full of dirt! It turned out to be a leaking rocker cover gasket dripping oil on to one of the ignition wiring connectors.




It's not the lambda sensor! This evening I connected an oscilloscope to the lambda sensor, and after the initial startup of the engine, the voltage starts switching between 0V and 0.62V with a period of a couple of seconds.

So the regulator loop, including the sensor works!

http://www.wps.com/LPG/o2sensor.html (very informative!)

Revs dip with the output voltage => lean mixture, dipping revs...
Why do revs dip with lean mixture?

I have no air leak, it was the pump I was hearing. So it's probably too little fuel... fuel pump.... it's very noisy, maybe too low fuel pressure...?

Next step is one of:

1. Try another fuel pump
2. Have the fuel pressure measured

Comments anyone???
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Anders Dinsen
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« Reply #4 on: December 14, 2004, 09:55:00 pm »

Aherm, well no, that is, not yet...  Grin

I guess that should be on my list. Thanks for reminding me. The computer *is* asking for a download of fault codes, but when I got the car, the wire to the water temp sensor was broken, that's probably the fault it's wanting to tell us about.

I don't think the computer can see an air leak or a too low fuel pressure, do you?

Could you see the dripping oil on the computer screen? (just kidding!)

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'82 Murena 2.2 prep 142
'01 Grand Espace 24v
'08 Smart Fortwo 0,8 cdi
mikehally
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« Reply #5 on: December 14, 2004, 10:31:54 pm »

I owned a Volvo 480 with fuel injection for many years and had recurring problems with unstable idle.

The fuel injection diagram had something called the "idle speed regulating valve" which looked like a clue. It opens and closes to regulate the amount of air at idle and control the idle speed.  It was prone to clogging up (enough to stall the engine, or make it race at idle) and I got used to cleaning it out with "carb cleaner" spray.  Eventually I got fed up and fitted a new one -- that cured the problem permanently.

Out of interest I took apart the old valve -- it consisted of an armature (like a motor) inside a magnet.  The clearance was very small indeed and the armature was rusty, so it was sticking.

A quick Google check reveals this is a known problem on Espaces too -- see http://dinsen.net/espace/teknik/j11-j63/fuelinjection.  Quote "One frequently encountered source of problems with this engine is the idle speed valve."  He then goes on to describe your symptoms.

Best of luck, Mike Hally
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Anders Dinsen
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« Reply #6 on: December 15, 2004, 06:59:57 am »

Thanks Mike for your input. It's me who has written the stuff on dinsen.net (go to dinsen.net/anders and you will find...me)... I'm quoting others, not my own experience though.

I think my idle speed valve behaves ok. It seems to open and close correctly and rapidly.

The Volvo 480 has the same Renault engine as the J117, is that not so?

- Anders
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'82 Murena 2.2 prep 142
'01 Grand Espace 24v
'08 Smart Fortwo 0,8 cdi
Will Falconer
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« Reply #7 on: December 15, 2004, 07:50:22 am »


I don't think the computer can see an air leak or a too low fuel pressure, do you?


No, but the computer did tell the mechanic to look at the ignition rather than fuel systems.
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mikehally
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« Reply #8 on: December 15, 2004, 11:03:59 am »

Hi Anders -- I doubt a visual check is conclusive.  Mine [when faulty] still worked but because it was sticky it didn't pass the correct amount of air.   And yes I think it was the same engine as yours -- that sodding idle valve certainly looks familiar!

But I'd strongly endorse the other replies that suggest a computer diagnosis -- there's a host of other possibilities.

Thanks Mike for your input. It's me who has written the stuff on dinsen.net (go to dinsen.net/anders and you will find...me)... I'm quoting others, not my own experience though.

I think my idle speed valve behaves ok. It seems to open and close correctly and rapidly.

The Volvo 480 has the same Renault engine as the J117, is that not so?

- Anders
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Anders Dinsen
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« Reply #9 on: December 18, 2004, 11:48:36 pm »

I've made a booking with a workshop specialised in engine electrical systems on January 11th for a diagnosis and measurement of fuel pressure.

I've discussed the matters on the Matra mailing list too, and the idle valve has been suggested as the source of problems there too.

I'll see if I can take an extra look at the valve tomorrow.

Thanks for all the input!
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'82 Murena 2.2 prep 142
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'08 Smart Fortwo 0,8 cdi
Anders Dinsen
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« Reply #10 on: December 19, 2004, 03:56:49 pm »

Hi Anders -- I doubt a visual check is conclusive.  Mine [when faulty] still worked but because it was sticky it didn't pass the correct amount of air.   And yes I think it was the same engine as yours -- that sodding idle valve certainly looks familiar!

Hmm, you are probably right. I sprayed wd40 in the valve. It did actually change the behaviour and idle speed was lowered slightly...
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'82 Murena 2.2 prep 142
'01 Grand Espace 24v
'08 Smart Fortwo 0,8 cdi
Anders Dinsen
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« Reply #11 on: December 22, 2004, 08:21:10 pm »

Today I replaced this idle valve:




with this one:



Notice how clean the new one is. The old one is very dirty and moves uneasily. I will try to clean the old one.

It did improve things noticably, but theres still some instability in the idle and idle speed remains so far at just below 1000 rpm.

Let's see if it improves over time or the computer needs to have error codes cleared before it changes - or if fuel pressure is just too low. 'Till January.

Happy Christmas to all!

- Anders
« Last Edit: December 26, 2004, 08:56:26 pm by dinsen » Logged

'82 Murena 2.2 prep 142
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kev2002
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« Reply #12 on: May 01, 2005, 08:21:39 am »

I have a 1996 espace and I had the idle speed vavle replaced by a spare part (not new) The old one was simply failing to open/close. This one I now have operates perfectly when the engine is at running temp. but it is erratic and stalls when cold. I have a friend at work who replaced this part on his espace with a new one at he still has the idle speed problem.  I had previously (with the old idle valve on) had the car checked by computer at the garage and they said I needed the valve changing but nothing else was faulty. Now I just have the idle speed raised a bit so it doesn't stall so much. What else causes this problem?

Thanks
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Anders Dinsen
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« Reply #13 on: May 01, 2005, 09:12:38 am »

I have a 1996 espace and I had the idle speed vavle replaced by a spare part (not new) The old one was simply failing to open/close. This one I now have operates perfectly when the engine is at running temp. but it is erratic and stalls when cold. I have a friend at work who replaced this part on his espace with a new one at he still has the idle speed problem.  I had previously (with the old idle valve on) had the car checked by computer at the garage and they said I needed the valve changing but nothing else was faulty. Now I just have the idle speed raised a bit so it doesn't stall so much. What else causes this problem?

Thanks

Check for bad sensors, especially the water temperature sensor.  Also air leaks in the inlet manifold may cause unstable idle. Check the fat pipe running from the engine top to the manifold. But since it's only when it's cold, check the water temperature sensor first and make sure you measure it by the computers connections to ensure that the wirering is okay.

Anders
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kev2002
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« Reply #14 on: May 01, 2005, 08:45:03 pm »

Water temp. sensor. I expect this can only be checked via one of those computer thingies? I think that is going to have to wait for now. However, as you suggest, it does seem to follow a logical course. I have recently had all the inlet manifold gaskets replaced so that is most likely ruled out. I appreciate your advice and suggestions. I have also left a post regarding fuel and would value your feedback on that, too. Cheers Anders.
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