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Thread: Renault Clio Misfire

  1. #1
    Join Date
    Dec 2007
    Posts
    8

    Unhappy Renault Clio Misfire

    I have a really annoying problem with my 1.2 Sreg Clio (8 valve).
    The car stopped the other day when my wife was driving it and it wouldn't start again. The wonderful RAC came out to the car and diagnosed the problem as a coil pack fault which had blown the fuse for the ECU.
    So off I went the next day and aquired a new coil pack.

    This appeared to cure the problem so continued to drive the car until suddenly it started running on 3 possibly two cylinders.

    I purchased some new plugs and leads but still there was one spark plug not firing. I checked that the plug was actually firing by placing the body of the plug on the engine block whilst connected and proved that it wasn't!
    My next course of action was to check the wiring coming into the coil pack.
    This was when I noticed that the cable had been fitted by my local garage the wrong side of the heat shield a few days ago after working on the gearbox selector. The result was that the wiring had suffered heat damage from the cat. Although I couldn't see it, I could feel the protective sheathing crumbling in my fingers!
    I managed to get the car to limp back to the garage and told them my concerns regarding the wiring, fully expecting the repair to cure the firing problem.
    Unfortunately it hasn't.

    My question is: Would the Crank Position Sensor cause these systems if it was on it's way out, or does anyone have any other suggestions as to what the problem might be?

    Thanks in anticipation!

    Steve.

  2. #2
    Join Date
    Sep 2007
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    80

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    Crank position would cause bad running but usually they only play up a couple of times then fail.

    Was the coil pack brand new? You may have a faulty fuel injector...

  3. #3
    Join Date
    Oct 2006
    Location
    Sussex
    Posts
    1,824

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    If you had a wire chaffed it could have blown the ecu. I would check the injectors are switching and that the coils/coilpack is being switched-if the coil pack is not being switched and there are no more wiring faults-it could indicate the ecu. Also you could recheck the fuse/fuses just in case.

  4. #4
    Join Date
    Dec 2007
    Posts
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    Thanks for that guys.
    The Coil Pack is brand new and it is only one plug that isn't firing.
    If the ECU is out, wouldn't that stop the engine altogether?

    Steve.

  5. #5
    Join Date
    Oct 2006
    Location
    Sussex
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    Not if the driver for the coil pack is blown is it only cyl no 1 that is not firing or is cyl no4 affected as well. Like I said above you need to determine if the coil is being told to fire by the ecu if it is we can rule the ecu out. Bear in mind that this is a wasted spark system-if its the one I'm thinking of so the coil will get two signals one for 1+4 and one 2+3.
    If the coil is not being switched I would think it would affect the cylinders in pairs but check first to rule it out.As I said above it could be a wiring fault if the loom has been damaged.
    Last edited by Sussex Patrol; 07-12-07 at 19:52.

  6. #6
    Join Date
    Dec 2007
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    8

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    Quote Originally Posted by Sussex Patrol View Post
    Not if the driver for the coil pack is blown is it only cyl no 1 that is not firing or is cyl no4 affected as well. Like I said above you need to determine if the coil is being told to fire by the ecu if it is we can rule the ecu out. Bear in mind that this is a wasted spark system-if its the one I'm thinking of so the coil will get two signals one for 1+4 and one 2+3.
    If the coil is not being switched I would think it would affect the cylinders in pairs but check first to rule it out.As I said above it could be a wiring fault if the loom has been damaged.
    Hi there,

    I have re-checked the sparks arriving at the plugs and it does appear that 2+3 are receiving very little from the coil pack!
    Does this then point to the ECU?
    I have managed to locate a good used one and fitted it but, the system now indicates an immobiliser problem (flashing signal on dash)! Am I right in thinking that the ECU is coded for each car then? Can this be overcome without spending a mint at Renault?
    Any help appreciated Sussex Patrol!

    Cheers,
    Steve.

  7. #7
    Join Date
    Oct 2007
    Location
    Middlesex
    Posts
    8,509

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    If the local garage caused your problem by incorrect repair, have you been back to them? What response did you get?
    A suggestion: Rather than taking the plug out to check for a spark, get hold of a plug tester. This fits between the plug and the lead and will give a visual indication of spark under normal running conditions. Bear in mind that when cranking, if you expel a flammable mix of petrol/air through the plug hole, and it ignites, you could be severely burnt! Also, a NOID light is a very useful diagnostic tool for checking coil and injector switching. You can pick both items up at any good auto-electrical retail shop.

  8. #8
    Join Date
    Dec 2007
    Posts
    8

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    Hi Rolebama,
    I used a plug tester. 1 and 4 plugs were illuminating brightly but 2 and 3 were very weak and could only just see a small glow.
    When I took the vehicle back to the garage with the burnt wiring, they said that it was just the outer hard plastic conveluted sheathing that had melted and that the four signal wires were in tact. They re-routed the cable to the correct side of the heat sheild before I had chance to check it for myself.
    There was no apology from them and they more or less washed their hands of the car. There last comment was "back to the drawing board then", and offered no help interms of diagnosis, even though it's a fair bet that the melted sheathing etc. could have been the reason the fuse initially went controlling the ECU!
    Loss of faith in the company is an understatement.

    Steve.

  9. #9
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    Might be worth replacing the lengths of the signal wires where the sheath was burnt. If the copper cores are 'cooked', you may be getting insufficient current to the coil. This could reduce the spark intensity.

  10. #10
    Join Date
    Dec 2007
    Posts
    8

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    Quote Originally Posted by Rolebama View Post
    Might be worth replacing the lengths of the signal wires where the sheath was burnt. If the copper cores are 'cooked', you may be getting insufficient current to the coil. This could reduce the spark intensity.
    Hmm, that's a thought, I'll give that a go.

    Cheers.
    Steve.

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