Renault Scenic Annoyance
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Thread: Renault Scenic Annoyance

  1. #1
    Tadpole pieterm's Avatar
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    Default Renault Scenic Annoyance

    I have had a continuing & frustrating problem with my 2001 Scenic. It will, without warning, drop into default or simply stall. Other times the revs will surge between 2500 and 3000 up and down. In either case pressing the throttle has no effect. Often, the car will be difficult to start requiring the ignition to be switched off and on several times before it will start. So far, and following the fault codes, the throttle potentiometer, throttle body and catalytic converter have been replaced all to no avail. Any help would be very much appreciated and save me from the crazy farm !!! LOL Thanks

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    Meant to add ... if I disconnect the MAP sensor then reconnect, all is good for an hour or so or until I turn off then need to restart the car.
    Last edited by pieterm; 31st October 2015 at 03:28 PM.

  2. #2
    1000+ Posts REN TIN TIN's Avatar
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    Sounds like the EMC is getting the wrong signals from somewhere, maybe the Oxygen sensor, TDC sensor, airflow sensor, etc.
    Check the connections to the EMC and the sensors. After 14 years it's possible one or more connections are dirty and have a high resistance or are open circuit.
    I take it you've had the car looked at by a specialist Renault mechanic not the local Ultratune or K-mart?
    If you haven't that would be a good place to start.
    "I cannot help but notice that there is no problem between us that cannot be solved by your departure. Mark Twain"

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    1000+ Posts jo proffi's Avatar
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    Quote Originally Posted by pieterm View Post
    …..So far, and following the fault codes, the throttle potentiometer, throttle body and catalytic converter have been replaced all to no avail.

    Quote Originally Posted by REN TIN TIN View Post
    I take it you've had the car looked at by a specialist Renault mechanic not the local Ultratune or K-mart?
    If you haven't that would be a good place to start.
    Sounds like a renault dealer fix so far.


    That bit about the map sensor….

    I only have a 'generic' understanding of EFI, and have never worked on a car with electronic throttle (my scenic has a metal cable connecting the pedal to the the throttle), but i do know that an erroneous map sensor reading will cause some weird stuff to happen as the ECU thinks the engine is at a different load than what it really is. Can explain difficult starts.


    I dont really care much about fault codes, as with my generic ecu about thirty of them can be generated in one misread of the crank/cam sensor.


    If i were in your shoes, i'd be trying to find some type of reader that shows real time ECU data, and take a look at what the various sensors are reading AT THE ECU whilst the engine is running .

    This test is a comprehensive test and not only tests the various sensors, but also the wires and connectors, which history shows are a common weak point on our beloved Renaults.

    If you break it down to idiot basic level, reving at 3000rpm shows a decent amount of air is being fed to the engine.
    The question is, why that amount of air?


    jo
    Last edited by jo proffi; 2nd November 2015 at 12:21 PM.

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    Fellow Frogger! Only19's Avatar
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    Have had a similar problem (twice) with an auto 2005 Clio - duff fuel. Drained tank and replaced with 98 octane. (And no longer go that servo!). Solved both times. Followed a third time with some similar symptoms that draining/refilling the tank did not fix. That time it was the throttle pedal!

    Cheers
    Bryce
    Who needs brakes? They only slow you down ....

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    Tadpole pieterm's Avatar
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    Thank you everybody for your much valued advice. The problem disappeared as quickly as it came proving, once again, that Renaults have character Maybe replacing the cat did fix it but it took a little time for previous gunge to get out of the system and allow the computer to correct itself ??? Thanks again, Pieter

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    Hi Pieter,
    I fully understand your frustration at this fault continuing in spite of all the money you have thrown at it.

    My 2002 laguna 2 manual 2 litre has/had the same problem. I was told there is no cure. You have a winter car. Park it for the summer!

    My thinking led me to a simple solution which, so far, has worked the last 6 times. Based on the theory that it is a heat-related fault, I spray the accelerator pedal box with Wolfchester Icebreaker Penetrating Spray, & within 2 or 3 minutes all is well and I am away as normal.

    It may be a month or so until it happens again in the warmer months. It has been fine since last autumn. Worth a try, and not expensive.

    Good luck

    John

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    Tadpole pieterm's Avatar
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    Thanks, John ... after announcing that all was well, it decided to 'shut down' at the traffic lights not an hour after my final message on this forum! Simply stalled and was difficult to start after. GRRR. So it's back into the garage. I've passed on your thoughts to the mechanic who simply raised his eyebrows in an "it's a Renault, what do you expect" excusing glance I've had a Renault 10, 12, 19, Laguna ('95 4 cylinder model)and this Scenic. The old cars never a problem. Both the Laguna and Scenic a pain in the **** and an open money pit. I still have the 19 which continues to be as reliable as ever and, being a non-computer (more-a-less) is not difficult to fix myself yet has all the options like a more modern vehicle. Problem is the Scenic is perfect for my family and it's the wife's joy ... she loves driving it. Lots of space yet easy to park. Hopefully, the mechanic will solve the issue quickly as we're sorta beyond the point of no return, now. Thanks again for your advice, John. I'll keep everyone updated and if anyone else has any ideas, please let me know. Kind regards, Pieter.

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    1000+ Posts jo proffi's Avatar
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    Get an rx4 scenic
    No electrical throttle or pedal and no issues.

    I knew you problems were not solved and youd be back.

    My cat disintegrated and apart from loosing a bit of economy snd low rev power it has displayed no other effects.

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    hi pieterm,
    Is your scenic an rx4 or 2wd? why I ask is that we have had two rx4,s and one began giving same symptoms as yours and detected the cause as a faulty vacuum switch on right front corner of inlet manifold,it has a three pin plug connector on it.I initially removed plug and found spring loaded plunger sticking,by moving position of plunger it varied idle.swapped with valve from other car and problem solved.just a thought if it is rx4 it may be the cause,good luck, jim
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    Based on the car being hard to start after the last failure, I'd try replacing the crank angle sensor. They seem to wear out and are only about $95. Mine was difficult to start for many months, and then flatly refused to fire and had to sit in the driveway until I put the new sensor in it. That fixed it.

    Also, have a look at the stiff plastic vacuum hose (about 6 mm diameter) attached to the top of the inlet manifold. Mine has a broken clip in it, so it eventually works its way loose. That will let extra bits of air in at times, making the engine run faster than the computer expects. (Oddly, if the hose comes off completely, the engine will rev to the limiter and the computer won't notice anything wrong).

    But the one final thing I had to do to my Scenic was related to the wiring. My car had been (badly) fitted with an aftermarket cruise control unit before I bought it. Does yours have one too? Mine was patched (or hacked, rather) into the wiring to the pedal potentiometer. The poor wiring (and poor design of the cruise control) destroyed two potentiometers over several years of infrequent use of the cruise control. After that, and sick of the constant stalling and error codes, I removed the cruise control's wiring to the pedal potentiometer and repaired the original wiring. The problem has gone away and I have declared it FIXED. This will only be of help to you if you have a nasty cruise control unit hacked into your wiring loom, but if you do, have a look at it.

    I guess it could also apply if there's other damage to the wiring to your pedal potentiometer. That thing is poorly built, poorly located and poorly integrated with the wiring loom. It was clearly shoe-horned into a car design that had previously used a mechanical throttle linkage.
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  11. #11
    1000+ Posts jo proffi's Avatar
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    Quote Originally Posted by Philip76 View Post
    Based on the car being hard to start after the last failure, I'd try replacing the crank angle sensor. They seem to wear out and are only about $95. Mine was difficult to start for many months, and then flatly refused to fire and had to sit in the driveway until I put the new sensor in it. That fixed it.
    A clean of the TDC sensor might also be a good first step.

    I've never seen one go cactus, but have seen gruby ones give week/poor signals.

    On the subject of the cracked vacuum line and redline revs..... Curious to know if the revs were generated by the extra air from the cracked pipe, or were they a result of the throttle being opened by the ecu?
    If it were the latter, and you actually saw those revs with the engine under load, i'd be very concerned with the programming of the ecu.

    On my antiquated fuego EFI (renix or aftermarket with cable throttle and MAp based load sensing) when extra air is ingested at idle from somewhere, and the revs increase as a result, sooner than later the engine will cough and splutter as it runs out of fuel, untill the revs drop back down to close to idle, where it will surge up again. The computer is still fueling from the idle fuel/ignition map.

    Pretty much the same as when the TPS is faulty (reading closed) and the ECU thinks it should fuel for idle.....ie bugger all fuel, so you accelerate, get to a few thousand RPM, then the engine dies from fuel starvation untill the revs drop and you can do it all over again.

    On this system, When actually driving the car at load, a crack in the MAP sensor pipe makes the ECU think it is running at WOT or at least a much higher load than reality, and massively over fueles and under ignition advances the engine, making o2 reading run stupidly rich and robbing performance in a massive way. Probably fouls the plugs very quickly too.

    Jo

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    Member Philip76's Avatar
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    I hadn't seen a TDC sensor break either, but it finally happened and my mechanic advised he'd been seeing it a bit lately, so had started importing them himself.

    That revving situation did concern me, for the reason you mentioned. The car still responded to the accelerator pedal, so I'd say it wasn't opening by itself. But it was still providing enough fuel to run as though the throttle was nearly fully open. This suggests to me that it was detecting excess air in the exhaust (due to the inlet leak), then adding more fuel to make the mixture richer, which of course kept it running fast. For some reason, it wasn't programmed to smell a rat when exhaust oxygen went up without the throttle opening wider, and was happy to add fuel instead of reporting an error. The result was a car that was dangerous to drive - I had to ride the brakes all the way home, nearly overheating the engine and transmission (and brakes) the whole time, except on 100 km/h roads. Plugging the vacuum hose back in fixed the problem instantly. I submit that the engine controller is programmed in an unsafe manner.
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  13. #13
    1000+ Posts jo proffi's Avatar
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    Quote Originally Posted by Philip76 View Post
    I hadn't seen a TDC sensor break either, but it finally happened and my mechanic advised he'd been seeing it a bit lately, so had started importing them himself.

    That revving situation did concern me, for the reason you mentioned. The car still responded to the accelerator pedal, so I'd say it wasn't opening by itself. But it was still providing enough fuel to run as though the throttle was nearly fully open. This suggests to me that it was detecting excess air in the exhaust (due to the inlet leak), then adding more fuel to make the mixture richer, which of course kept it running fast. For some reason, it wasn't programmed to smell a rat when exhaust oxygen went up without the throttle opening wider, and was happy to add fuel instead of reporting an error. The result was a car that was dangerous to drive - I had to ride the brakes all the way home, nearly overheating the engine and transmission (and brakes) the whole time, except on 100 km/h roads. Plugging the vacuum hose back in fixed the problem instantly. I submit that the engine controller is programmed in an unsafe manner.
    I dont like the sound of any of this.
    Jo
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