Scenic Woes
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Thread: Scenic Woes

  1. #1
    1000+ Posts REN TIN TIN's Avatar
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    Default Scenic Woes

    At the beginning of the month I had my Scenic (F4R + DP0) in for it's annual major service ("C" service I think). There wasn't anything major wrong and the only issue was a possible overheating of the gearbox.

    When I picked it up after the service and I was a few meters down the road it started running very rough (like it was flooding or too much choke), was threatening to stall and had bugger-all pulling power. I drove it back immediately but because of one-way streets I had to do a loop of a kilometer or two. When they took it for a test drive if ran faultlessly, maybe it had warmed up a bit and the fault cleared. The next day it stalled on me and cut out completely but after a restart appeared to run okay and didn't stall again. The fuel consumption is also a lot higher. It's always been bad but averaged in the mid 10's for mostly city driving. It was now, albeit after only a short time, averaging in the mid to high 11's.

    I've had it back to the workshop twice now and it's running a tiny bit better (not running rough or stalling when cold) but the fuel consumption is still in the mid 11's and it seems to run out of puff over 110kph or thereabouts or going up hills etc. Basically doesn't have anything over 3500RPM. According to the current consumption on the trip meter, fuel consumption is okay on light or medium throttle settings, but plant the right foot and meter runs into the 20's (or more) very quickly.

    Given the workshop said they have checked and eliminated all the obvious possibilities (e.g. dirty plugs, blocked airfilter, dirty TDC sensor, etc. The only thing they found that might have caused the issue was an oxygen sensor which was replaced (at my considerable cost). The CLIP didn't turn up any error codes.

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    I'm not a mechanic but I'm guessing two possible problems;

    1. Dephaser kaput. The dephaser has always been noisy for a few seconds on startup (like a diesel noise) but this is not uncommon and supposedly doesn't affect the operation of the motor. If the dephaser (or the controlling solenoid or EM computer) has given up the ghost completely would it affect the timing so much that it would noticeably affect the power and fuel consumption. My understanding of the dephaser is that they just advance the opening of the inlet valves by a few degrees at higher revs. (I guess it has to make some difference or the car companies wouldn't waste money fitting the things)
    2. Blocked cat and/or exhaust. This will of course affect the power and fuel consumption, but short of removal and replacement, how do you test a cat?


    Both these options can be eliminated by replacing the suspect component but cats aren't cheap and Renault ones are even more expensive. The dephaser is a big buck item to source and replace and means timing belt too (it due next year). To replace both I won't see much or no change from a couple of grand.

    PS. The workshop is a specialist French Car workshop so do know their Renaults.

    PPS. I have to get any major work done by mechanics or workshops there days. My hands don't work as well as they used to due to arthritis so I'm up for labour costs. And the cars live outside so all work has to be done on the driveway. i.e. not night time or rainy days (or extremely hot days either).

    Your thoughts.

    Cheers
    RTT
    "I cannot help but notice that there is no problem between us that cannot be solved by your departure."

  2. #2
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    Ren, the cat went in my 206 not long after I bought it. The main symptom was a significant reduction in power. It would occasionally run OK but not for long. I guessed it was the cat as there was a bit of a rattle. What happens is the ceramic substrate breaks off and moves to block the outlet, but can move around so it varies the amount of restriction. A new cat made a huge difference. There were no error codes given by the ECU/BSI. Sometimes it would barely go at all.

    I just had a generic high flow cat fitted, US made in stainless.

    Here's the thread about it if you're interested.

    206 GTi - blocked cat or coil issue opinions
    Last edited by Stuey; 23rd March 2018 at 12:01 AM.


    2003 PEUGEOT 206 GTi

  3. #3
    1000+ Posts REN TIN TIN's Avatar
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    Hello Stuey,

    Yes, I'm leaning toward exhaust issues.
    My symptoms are similar (except for the rattle) but aren't as bad as you describe but then the cat might not be blocked as much too.
    Fuel consumption is up by about 10% and it does run okay(ish). I mean it idles okay and does get up 100 - 110 k/h but it doesn't feel like there's much more the engine can give even though it's only pulling about 3000 - 3200 RPM. One's foot it virtually on the floor (drive by wire). It's when accelerating that the rough running happens but it's only temporary and usually when the motor is cold. There are no error codes coming up according to the mechanic and no warning lights on the dash.

    Replacing the cat won't hurt anything except my wallet (I'm guessing at least $500 supply & fit). There's an exhaust shop that's about 5km from me that I have used a few times before that are pretty good. (Last time I was there he was making some custom headers for a V8 thingumabob). They did the rear muffler on my 12 so don't mind 'odd' marques. The issue is going to be to find the time to get there. Football season means no Saturdays. So only Sundays and no auto workshops or exhaust shops are open on a Sunday.
    Why can't there be 8 days in a week. 5 days to work, 2 days for week-end/family/sport, 1 day for cars/ veg-out. (Of course everything has to be open 8 days a week too).

    Cheers
    RTT
    "I cannot help but notice that there is no problem between us that cannot be solved by your departure."

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    It happened immediately after a service. What are they offering, as it was OK before?

    Why would a catalytic converter suddenly do this?

    Good luck.
    JohnW

    Renault 4CV 1951
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    Hi Ren Tin Tin
    It could be the cat, put it out side with a good talking to
    The test for a blocked cat is to pull the O2 sensor out and fit a pressure gauge and measure the pressure in the exhaust. I guess there is not a plug fitted for that. Not sure what the pressures are but Google would know ?? Often they whistle or hiss when blocked and you go hard but not easy to hear from inside possibly.
    Jaahn

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    Yeah, I posted in that thread that mine had a wheezy sound. Mine did happen all of a sudden, too...it wasn't gradual.


    2003 PEUGEOT 206 GTi

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    I might be talking through my hat here, I don't know if it is relevant or not....

    My Pug 307 Diesel behaved similar to the description above - performance down overall, sometimes OK, other times woeful. Fuel consumption was noticeably worse - getting 6s and 7s instead of 5s.
    turned out to be mass air flow sensor - a new one fixed it instantly. They can be just dirty, or can be stuffed. Mine was stuffed.
    I have no idea if petrol cars also have a MAF sensor - I'd guess yes? The injection computer needs to detect how much air is flowing into the manifold to know how much fuel to squirt, if the MAF sensor is giving wrong readings or no data, then the computer will send the wrong amount of fuel or fall back to fail safe data. (the priority of which is to get you home, not best performance and consumption.)

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    It does seem weird it was straight after a service.


    2003 PEUGEOT 206 GTi

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    1000+ Posts jo proffi's Avatar
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    Quote Originally Posted by simca1100 View Post
    I might be talking through my hat here, I don't know if it is relevant or not....

    My Pug 307 Diesel behaved similar to the description above - performance down overall, sometimes OK, other times woeful. Fuel consumption was noticeably worse - getting 6s and 7s instead of 5s.
    turned out to be mass air flow sensor - a new one fixed it instantly. They can be just dirty, or can be stuffed. Mine was stuffed.
    I have no idea if petrol cars also have a MAF sensor - I'd guess yes? The injection computer needs to detect how much air is flowing into the manifold to know how much fuel to squirt, if the MAF sensor is giving wrong readings or no data, then the computer will send the wrong amount of fuel or fall back to fail safe data. (the priority of which is to get you home, not best performance and consumption.)
    I don't think you will find a MAF sensor on a renault. They use MAP to gauge load. A leak in the small hose that connects the inlet to the MAP sensor will certainly cause a bad state of tune.

    If RTT had a diagnostic device, some of the guess work can be sidestepped.

    Jo

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    Isn't a broomstick one of the recognised ways of fixing a blocked ceramic 'cat?
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    Quote Originally Posted by Simon View Post
    Isn't a broomstick one of the recognised ways of fixing a blocked ceramic 'cat?
    Bit of steel rod. Broom stick won't hack it.
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  12. #12
    1000+ Posts REN TIN TIN's Avatar
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    I don't know if it is the cat, just a guess at this stage in the absence of other possibilities.
    But looking on the net, a cat is around EUR700 plus fitting, even more if buying from Renault. So maybe a bit more investigation might be prudent before I get the cat done. Maybe the broom handle/ iron bar/ 2 inch spade bit might be a temporary 'repair' for the cat if it is faulty. The cat looks fine from the outside, no dents or rust holes but I guess they all do even if the inside has disintegrated.

    No, I don't have any diagnostic equipment but I took it back twice and the workshop hooked up the diagnostic equipment (Clip etc.) looking for errors. So whatever parameters could be tested with the equipment were tested and eliminated (only thing found was an possible dodgy oxygen sensor and that was replaced but didn't improve anything). A leak in the vacuum hose probably wouldn't come up on the diagnostic device and it's possible a hose was disturbed during the service. They had to access the air filter, spark plugs, etc. during the service so a pipe or sensor getting disturbed is quite possible (and is what I was hoping for). Or there's a bad connection to one of the plugs on a sensor. But again, which one.
    But I wasn't there so they could have parked the car in the workshop for a day, did nothing and just said they checked it out or they could have gone through everything like they said turned up nothing. I trust them so like to think it was the latter.

    I think I might get a Moped. You can buy a new motor for under a hundred bucks so if it stops running just replace the whole engine.
    "I cannot help but notice that there is no problem between us that cannot be solved by your departure."

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    Hi Ren Tin Tin
    Go to your local exhaust fitters and get some prices for a generic cat fitted. Be a lot cheaper than that I think. They just cut it out and welds in a new unit like an after market muffler. My daughters car's cat fell apart inside and sometimes blocked the outlet and no power, but most of the core was gone when it was replaced by an after market one.

    The problem with the diagnostic readers is that mechanics rely on them to say what all problems are but in reality there are a lot of problems which do not show on a sensor so they are left with no answer. They should do a simple 'manual' diagnosis first using basic principles, but they do not know how now
    Jaahn

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    1000+ Posts jo proffi's Avatar
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    Quote Originally Posted by REN TIN TIN View Post
    So whatever parameters could be tested with the equipment were tested and eliminated (only thing found was an possible dodgy oxygen sensor and that was replaced but didn't improve anything). A leak in the vacuum hose probably wouldn't come up on the diagnostic device and it's possible a hose was disturbed during the service. .
    If the leak was on the circuit to the MAP sensor, it will show on the sensor.
    It may not send up an idiot light that says..Hey Idiot check the MAP sensor or its hoses, but if the user had some idea of the MAP pressure at idle and at also WOT (ambient atmospheric Air pressure) and what to expect in between, they might gain some idea by watching how the MAP relates to TPS.

    Jo

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    Quote Originally Posted by jaahn View Post
    Hi Ren Tin Tin
    Go to your local exhaust fitters and get some prices for a generic cat fitted. Be a lot cheaper than that I think. They just cut it out and welds in a new unit like an after market muffler. My daughters car's cat fell apart inside and sometimes blocked the outlet and no power, but most of the core was gone when it was replaced by an after market one.

    The problem with the diagnostic readers is that mechanics rely on them to say what all problems are but in reality there are a lot of problems which do not show on a sensor so they are left with no answer. They should do a simple 'manual' diagnosis first using basic principles, but they do not know how now

    Jaahn
    During an exhaust system rebuild on my Xantia a few years ago, a large lump of cat core fell out of the exhaust pipe - from the section after the resonator!! This explained why the car's performance had been so variable - the lump of core had been on the move for some time and, depending on location and orientation was sometimes causing significant flow restriction.

    As jaahn says, this sort of problem does not trigger any codes, as there is no sensor for restricted flow etc...

    So my advice is to not just replace the cat - get the whole exhaust checked for restrictions!

    Cheers

    Alec

  16. #16
    1000+ Posts jo proffi's Avatar
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    Quote Originally Posted by jo proffi View Post

    If RTT had a diagnostic device, some of the guess work can be sidestepped.

    Jo
    Diagnostic Solutions: Exhaust Restriction Diagnosis - Tire Review Magazine
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  17. #17
    1000+ Posts REN TIN TIN's Avatar
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    Thanks guys.

    Yes, I'll take the car along to a exhaust shop after Easter.
    During the service they replaced one of the rear exhaust mounts, perhaps they dislodged a piece of the muffler internals and it's restricting the flow.
    It's still on it's original exhaust system from manifold to exhaust tip so probably could use a spruce-up.
    It can't hurt anything except my wallet and my spare time.

    A lot of workshops do rely on the computer diagnostics to tell them what's wrong.
    Got to find someone with grey hair that know how a IC engine works and can find problems without relying on a computer to tell them what's wrong. There aren't sensors on everything and computers aren't infallible.

    Jo, thanks for the link. Certainly sounds like some of the symptoms I'm experiencing, eg. lack of power going up hills.

    Cheers
    RTT
    "I cannot help but notice that there is no problem between us that cannot be solved by your departure."

  18. #18
    Too many posts! JohnW's Avatar
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    Any jack marks under the cat? Any deformation along the system?
    JohnW

    Renault 4CV 1951
    Renault R8 1965
    Renault Scenic 2005 (wife's)
    Renault Scenic 2007 (mine)
    Renault Scenic 2006 (daughter's)
    CitroŽn CX Pallas 1980

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  19. #19
    1000+ Posts REN TIN TIN's Avatar
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    Quote Originally Posted by JohnW View Post
    Any jack marks under the cat? Any deformation along the system?
    Hello John,

    No, nothing under the car, all looks as it should.
    Anyway, the mechanic had the car on a hoist 3 times this month so should have seen anything out of the ordinary.

    The rear muffler does look lacy though so we might be on the money with an exhaust issue.
    I guess the cat and the intermediate muffler run reasonably hot, even on short trips, so they burn off any condensation pretty quickly. The rear muffler is cooler so any moisture that doesn't get burnt off is going to stop there.

    Cheers
    RTT
    "I cannot help but notice that there is no problem between us that cannot be solved by your departure."

  20. #20
    Too many posts! JohnW's Avatar
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    Be interesting to see whether the exhaust work fixes it. If so, maybe it is just one of those coincidences.....
    JohnW

    Renault 4CV 1951
    Renault R8 1965
    Renault Scenic 2005 (wife's)
    Renault Scenic 2007 (mine)
    Renault Scenic 2006 (daughter's)
    CitroŽn CX Pallas 1980

    National Co-ordinator, Renault 4CV Register of Australia

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