Renault RX4 still having engine problems.
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  1. #1
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    Default Renault RX4 still having engine problems.

    G'day Renault Rx4 Enthusiests. Still havig problems with the engine. Simptoms are: Starts and idles, runs fora while OK. when requiring power from the engine around 2,000 rpms starts to miss and loose power. I turn the key off and restart after a short spell. It seems to run OK for a while and then starts playing up again. What I have done 1. Replaced the fuel pump complete. 2. Replaced the filter close to the tank. 3.Replaced the Spark plug coils with new ones. 4. Replaced the spark plugs. 5. Emptied the fuel tank and replaced with fresh fuel. 6. Bought a diagnostic tool and checked the computer for faults 'stored' reveled no faults or stored fault codes. Whats left ...... any ideas out there. Cheers

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  2. #2
    1000+ Posts jo proffi's Avatar
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    Check the throttle position sensor and manifold pressure readings in real time if the diagnostics allow this.
    MAP should read 100ish at wide open throttle and 30-40 at idle. If at moderate throttle it reads 100 or more, there is a crack in the vacuum line.
    It never hurts to clean the crud of the TDC sensor which is located in the bell housing.

    I'm not sure how the newer renault ignition and tacho gauge work, but on my old banger the dash gauge gets its signal from the coils so if there is an ignition problem it is often manifest in the tacho gauge also.
    Now that I think about it you probably have coil on plug, but if the tdc sensor is missing a heartbeat now and then , it still might show up on the Tacho gauge.
    Jo

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    Contented Peugeot Driver addo's Avatar
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    I'd suggest that unless you have a CLIP diagnostic tool or the counterfeit thereof, it may lack sufficient dialogue with the ECU.

    FWIW faults "upstream" of the engine ECU such as charge issues, don't always log a fault - or when they do it's a red herring like antipollution or ESP.

  4. #4
    1000+ Posts jo proffi's Avatar
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    Quote Originally Posted by addo View Post
    I'd suggest that unless you have a CLIP diagnostic tool or the counterfeit thereof, it may lack sufficient dialogue with the ECU.
    Well thats boring then.

    You want to see some of the fault codes my ecu throws up when the laptop loads up its software wrong.



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  5. #5
    Contented Peugeot Driver addo's Avatar
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    If you can see live parameters it does often help diagnose... I do a scan without running the motor, then preferably watch parameters from a dead cold startup. If you get good data from all sensors including the sensor supply voltages and charging voltage, it's time to check third party components like battery and cooling fans; anything with periodic heavy current draw that can cause an ECU to stumble.

  6. #6
    VIP Sponsor David Cavanagh's Avatar
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    Quote Originally Posted by richtind View Post
    G'day Renault Rx4 Enthusiests. Still havig problems with the engine. Simptoms are: Starts and idles, runs fora while OK. when requiring power from the engine around 2,000 rpms starts to miss and loose power. I turn the key off and restart after a short spell. It seems to run OK for a while and then starts playing up again. What I have done 1. Replaced the fuel pump complete. 2. Replaced the filter close to the tank. 3.Replaced the Spark plug coils with new ones. 4. Replaced the spark plugs. 5. Emptied the fuel tank and replaced with fresh fuel. 6. Bought a diagnostic tool and checked the computer for faults 'stored' reveled no faults or stored fault codes. Whats left ...... any ideas out there. Cheers
    You've done the TDC too haven't you? Wasn't it you who got a TDC off me?
    The only other thing we sell is throttle bodies. I don't know what goes wrong because we don't diagnose but we sell every one we get.
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    Yes David, I'm the bloke, I forgot at the time, yes I bought the TDC from you. Was wondering if the module would be faulty to cause this sort of problem? RT

  8. #8
    1000+ Posts jo proffi's Avatar
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    Quote Originally Posted by richtind View Post
    Yes David, I'm the bloke, I forgot at the time, yes I bought the TDC from you. Was wondering if the module would be faulty to cause this sort of problem? RT
    Which module would that be???

    If a TPS (throttle position sensor) is kaput, the engine computer will not know you've come off idle, and will be fueling for idle, hence it stumbles at 2000rpm.
    I've seen that happen on a few older renaults.
    Interestingley, on the laguna 1 it was a bit of a procedure to recalibrate the ecu to read the new TPS and simply changing it did not fix the problem entirely.
    Jo

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