Anders Dinsen
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« on: December 12, 2004, 07:46:31 am » |
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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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1982 Talbot Matra Murena 2.2 prep 142 2017 BMW i3 "Charged Professional" 94Ah
Used to own: 2001 Renault Matra Grand Espace "The Race" V6 24v 1997 Renault Matra Espace 2.0 8V 1987 Renault Matra Espace J11 2.2
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Anders Dinsen
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« Reply #2 on: December 14, 2004, 09:10:55 pm » |
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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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1982 Talbot Matra Murena 2.2 prep 142 2017 BMW i3 "Charged Professional" 94Ah
Used to own: 2001 Renault Matra Grand Espace "The Race" V6 24v 1997 Renault Matra Espace 2.0 8V 1987 Renault Matra Espace J11 2.2
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Will Falconer
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« Reply #3 on: December 14, 2004, 09:45:05 pm » |
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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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mikehally
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« Reply #5 on: December 14, 2004, 10:31:54 pm » |
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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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mikehally
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« Reply #8 on: December 15, 2004, 11:03:59 am » |
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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 #11 on: December 22, 2004, 08:21:10 pm » |
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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
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« Last Edit: December 26, 2004, 08:56:26 pm by dinsen »
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1982 Talbot Matra Murena 2.2 prep 142 2017 BMW i3 "Charged Professional" 94Ah
Used to own: 2001 Renault Matra Grand Espace "The Race" V6 24v 1997 Renault Matra Espace 2.0 8V 1987 Renault Matra Espace J11 2.2
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