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Discussion Starter #1
Hi,

So I have a 2010 1.5DCi Meange with 72k on the clock. The belt was changed at 63k.
Over the last year, mainly when the weather is warmer there's been some hesitation, most noticable when driving along and I then take my foot off the throttle, due to a corner or say going down hill. If I then put my foot back on the throttle I get hesitation best described as if I'm tapping the throttle peddle. If I release the peddle, then pause, then go back on it seems better.
As per the title there is, when I stop some air in the fuel pipe just after the priming bulb. I've changed the fuel filter, but this made no difference. Additionally, there is a strange clunk noise when I take my foot off the throttle, it's not always at the same time after taking my foot off, but is within a second or so. I did take off and clean the EGR valve last year, it was suprisingly clean. I have also unplugged the EGR connector and it ran better, the slight hesitation that there has always been on move off was noticably less.

So would anyone have an idea? I thinking of replacing the EGR valve as it looks like that could be at fault and maybe replcing the primer bulb, but that alone seems to cost £135 or so.

Cheers,

Marc
 

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Super Moderator Technical Supremo Platinum Member
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For the clunk I would look at engine mounts, especially rear "dogbone"

Hesitation, cannot discount EGR but if clean and disconnected, should not be an issue.
Air in fuel lines maybe.
Changing primer only needed if split or internal check valves jammed open.... the first may be letting some air in, the latter can be found by pumping it and seeing if it goes hard (ooh matron) but even if failed, will not be letting air in.
Air can be from fuel filter connections (common) a little grease can help.
Any joint
Any worn point on inlet pipes
Leaky injectors.
 

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Discussion Starter #3
Hi Technodad,

Thanks for the list. I think the term clunk might have been too harsh of a word, maybe partway between tick and clunk, maybe the sound you get if you flick a wooden desk.

I'll run with the EGR valve connector off for tomorrow, it's only a short journey to work.
I'll try getting the bulb hard too, I do remember pumping it before and lots of little bubble came out and joined the large bubble in the pipe.

With regards to leaky injectors, how would I check this?

Cheers,

Marc
 

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Super fantastic Mod Technical Supremo Nice Guy
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YOU will always have air pockets in a diesel system on tick over, its only drawing enough fuel as required..
If your car is starting ok, leave the fuel system alone..
Only if having problems starting, go for low fuel pressure side of the system for leaks..
 

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Discussion Starter #5
So after a run to and from work, nice warm weather, the car really did feel more lively. There was no slight hesitation on pull away and none after lifting off for a bit then going back on again. So would this be conclusive that the EGR valve is playing up? Is there a bench test for these to check their operation? The whole time the engine light was on (to be expected) but it said Check Injection System, is that normal?

Thanks
 

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Check injection, covers EVERY sensor on the engine ..
so on yours you have 4 injectors each with sensors.
A cam sensor, a crank sensor, a turbo boost sensor, a map sensor, throttle sensor, accelerator sensor, Egr sensor.
Infact anything electrical on your car, goes to a sensor of some type..
There area few more I have missed on the list, but all sensors, how ever they are described..
 

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So after a run to and from work, nice warm weather, the car really did feel more lively. There was no slight hesitation on pull away and none after lifting off for a bit then going back on again. So would this be conclusive that the EGR valve is playing up? Is there a bench test for these to check their operation? The whole time the engine light was on (to be expected) but it said Check Injection System, is that normal?

Thanks

Engine management light is normal for a disconnected EGR...reconnect and it should go out.
Check injection suggest something else but as Ourkid says, could be any sensor, even the EGR not moving meaning not enough air

I'm not happy with air bubbles and more being pushed in when you pump primer.... some is normal even if not desirable.
Getting more in when priming suggests a leak in the fuel feed system to me.
 

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Super fantastic Mod Technical Supremo Nice Guy
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If fuel line from the high pressure pump to the injectors are full, then the return will open up and air shows..
Get your car running, get someone rev it, and watch these bubbles vanish, at the same time pump the primer, no more will appear
Thats why I hate these clear pipes on the 1.5 dci, people see these bubbles and panic...
BUT all 1.5 dci engines do this..its how the return works..
 

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Which return Ourkid ???
Thought on the 1.5 returns went to filter and returned excess fuel so still not sure where the air is coming ?
Not questioning knowledge, just don't understand :crying2:
 

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On idle, The ECU measures the fuel rail pressure, this then switches the fuel pump off and on, so you now have small air pockets..
When underload and the request for more fuel is needed, then the system allows more fuel through,,,.
 

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Yeah okay.
ECU controls fuel pressure regulator at pump and calls for pressure as needed with excess fuel being bled off via returns.
But where does the air come from ?
It's nominally a sealed system with air being bled out by initial priming.
So if air in there it either hasn't got out or new air has got in.

Not panicking over air being there BTW, I know that some is normal.
But when coupled with issues like hesitation and Injector Fault, I have to wonder
 

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Its not Pete, Its only sealed to the fuel filter from the tank up, not the return, When the injectors are opening slowly fuel is sent back to the filter off the fuel injector leak off pipes, but the fuel pump is being switched off and on, so air pockets form in the return to the filter,, More efficient to send the fuel to the filter housing than the tank..
 

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Discussion Starter #13
Hi,

Thanks for all the advice so far. I've driven a couple of times with the EGR valve connector disconnected. It really does feel like a different car. No hesitation, mush smoother pulling away. Is there a way to test the EGR valve off of the car, although it seems to be the problem I'd still like to check. Can anyone recommend a suitable replacement? Mid priced valve at local Eurocarparts - Part Link

Cheers,

Marc
 

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Discussion Starter #14
Hi, so after putting the plug back on the car displayed 'Check anti pollution system'. It stayed on for a long while. Then didn't come on after a couple of drives. Does it point to a fault EGR valve even more?
 

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The sensor system on EGRs measures the travel when it opens and closes and compares that to stored levels (in ECU)
If the movement reading is not what the ECU expects, the warning comes up.
Stored levels are set via CanClip diagnostics but the system also self learns, if movement changes but then holds steady, it will use new levels.
Setting is known as setting adaptives.

From your descriptions, I suspect that the EGR was sticking, not closing properly and may have been full of gunk, so engine not breathing properly either.
A stuck open EGR is one cause of hard starting.
Having cleaned, some improvement but quite possible that EGR is now moving further, hence warning and because the system learns, warning going out.


If EGR is still sticking a bit, a new one is the way to go.
The hesitation etc and improvement when EGR unplugged is suggestive that it is still sticking.

Did you clean the inlet pipes when you cleaned the EGR... if they are gunked still, breathing will be impaired.


Testing.... older models so this may not be correct.
Treat as a guide not gospel.

6 pins
2 pins are power to motor, 12v.... were pins 1 & 5
Should be able to check on plug when engine running to find which pins give 12v to earth.
Pin 3 was not used
Pin 2 & 6 were either end of the measurement track
Pin 4 was the wiper and resistance should vary between Pin 4 and 2 or 6 when valve opens or closes.
12v across pins 1 & 5 on valve should open and close it but check got the right pins first.
 

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Discussion Starter #16
Hi Dancingdad, Thanks for the explanation for the faults I'm seeing. I'll take a look at the weekend to see if the pin-outs are the same.
I guess the self learning is why I'm not seeing the same level of hesitation, did you have any thoughts as to why? Cheers!
 
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