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Discussion Starter #1
Hi all,

I have recently purchased a 2007 Clio with the 1.2 TCE 100 engine, there is an odd issue with the PCV/breather pipework that I am trying to work out the solution to, I believe the actual PCV setup is in the rocker cover however my issue is the hoses on the engine. I think Renault call it the 'oil vapour rebreathing circuit' - I will probably look to change this to a catch can at some point though.

There is a hose going from the rocker cover over to the intake hose (before the turbo), there is also a smaller hose that tees off to the inlet manifold (guessing its using it as a vacuum source).

My issue is that a previous owner has snapped off and tried to reglue what I believe is/was a 1 way valve between the intake manifold and the hose going between the intake and rocker cover.

My issue is that if I just use a hose and connect up the inlet manifold and the tee line the engine stalls, the engine does run ok with the hose disconnected and I have noticed that if you remove what is left of the hose and connector on the inlet manifold the idle is higher.

I have bought an off the shelf check valve to try and see if replacing the broken 1 way valve fixes the issue as at the moment there is a vacuum/boost leak caused by the fact that the hose is open to atmosphere. I don't really want to boost the engine much as there would be a boost leak meaning that the turbo will be working harder to get the same level of boost in the pipework etc.

I don't know if this engine has a MAF sensor, I believe it runs on MAP sensors (I can see a couple of them) so shouldn't be too affected by unmetered air. It would seem that the ECU has adapted the fueling to take this extra air into account as I think the long term fuel trim (using an OBD reader) seems to be at around 30%!

Here are the different combinations of trying blocking/connecting up things I have tried so far to try and narrow down the issue:

Main hose connected, inlet manifold hose connected but not teed to main hose - engine runs but can hear the vac leak
Main hose connected, inlet manifold hose disconnected - engine runs at a higher idle and fluctuates showing the extra air messes with the idle
Main hose connected, tee hose open but inlet manifold blocked - engine stalls
Main hose connected, extra hose (no check valve) connected to the main hose tee and inlet manifold - engine stalls
Main hose connected, inlet manifold hose connected and then pushed together with the tee hose on the main hose - engine stalls

I am going to try and see if I can block off the tee hose on the main hose and see if blocking the inlet manifold hose still makes the engine stall.

I have a feeling that the engine might run ok with the inlet manifold hose blocked but due to the high fuel trims its running too rich to carry on running!

Can anyone confirm that the valve in the hose between the inlet manifold and the main hose is a 1 way check valve? Makes sense to allow for vacuum but not boost. Just seems odd that the engine would stall out if I blank off the intake manifold, only thing I can think of is that the t in the main hose between the rocker cover and intake hose before the turbo needs to also be blocked off.

Thanks in advance
 

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Discussion Starter #2
Just gone out and started the car again, on initial start up with the inlet manifold hose unplugged I simply put my finger over the end to block it off, the engine then dropped in idle and then readjusted back to a normal idle. When releasing my finger the extra air increased the idle and the engine then readjusted down slightly as before.

It would seem that when trying things yesterday when the engine was warm, the initial drop in RPM when the end is plugged caused the engine to stall out as the ECU would have set the throttle at a set position expecting that amount of air (with it leaking). With the engine cold the idle is higher as its on its warm up cycle so the drop in RPM when plugging the hose drops down but not low enough to stall the engine.

I will try and see if I can plug the hose when the engine is cold later for it to then relearn the correct throttle position for idle, hopefully it will then store this setting next time it starts up with the hose blocked off - I am guessing at the moment if I block the hose at the moment its learn a certain much more closed position as its starting position from when it was open meaning that if I block the hose now it won't be open enough to idle the car.

I will report back with what I find later.
 

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Discussion Starter #3
I have made a bit of progress on this, as the car seems to be ok with the pipe blocked off on cold start I simply blocked it off and let the engine come up to temp. I found that the engine did idle very low at around 650rpm which I believe is correct, when revving the engine it then dropped back down and settled at the RPM and was fairly smooth.

I then switched the engine off and on again (with the engine up to temp), the car then just stalled out and no longer idles which makes me think that it might be the idle control valve being slightly gummed up - as the higher temp would mean a lower idle and therefore a smaller gap.

I am going to swap out the plugs tomorrow anyway as a matter of course as I have some, I have heard that this can sometimes fix the issue, I think this is the first time that the car has idled at 650rpm meaning that its probably had a vac leak for a fair while and might be the reason why someone sold the car etc.

I have a 1 way check valve on its way as well - my main issue is that there will be a boost leak at the moment due to the hose in the intake, not too worried about a bit of extra air getting into the intake (as OEM I believe) via that hose as the ECU is adjusting the idle down.

I am going to change the plugs and check the condition, also need to change the oil and want to run some injector cleaner through the system - might look to take the throttle body off the car as well to give it a clean as the idle control port is on the back side of the throttlebody.

I have seen a fair few threads about idle issues with this engine or the no turbo D4f engine, seems to mainly be plugs, idle control valve, coil pack or wiring chafing it seems coupled with needing to reset the throttlebody to relearn.

I am also going to check to see what the long term fuel trim is, I recon its still very high which might mean that when warm the rich fuel mix coupled with older plugs and a low RPM coupled with a possibly slightly mucky idle control valve could mean the engine can't catch the engine as the revs drop down to idle.

I will report back to see what I find - the car drives fine, just need to sort out the boost/vac leak to keep the boost in the engine!
 

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Discussion Starter #5
Thank M1tch!
No worries, I figure its a common issue, the car idles and runs with the pipe disconnected as the idle control does adjust the idle down with its large vac leak. Ideally I want to block off the pipe to the intake manifold and install a catch can at some point. I have a feeling fitting a one way check valve will sort the issue initially as it will allow vacuum in on idle but then block off when it transitions into boost - I believe this is how it should run as OEM.

It's promising that the engine will run with it blocked off when its cold and coming up to temp though, I think the fact that the idle is set so low by Renault means that if anything isn't 100% clean then the delicate balance will be disrupted.

My '07 is on around 89k miles with 'uneven' service history - just had the cambelt, tensionors, waterpump and aux belt changed as a precaution (cheaper than a new engine!) - will change over plugs tomorrow and check the state of the current ones. I have a feeling they might still be original but will see if the electrodes are degraded at all - for anyone needing the numbers for the spark plugs they are:

Renault - 8200587901
NGK - ILKAR7A7

Looks like there are other alternatives as well:

BERU - Z274
Champion - OE225

I figure that as the engine does run ok with its current vac/boost leak the other sensors are ok, I did clean the MAP sensor in the inlet manifold as well, I think I saw another on one of the boost pipes I will also investigate and clean.

I will report back when I have sorted a few things out, I can see that the OEM check valve has been bodged as its been snapped off.
 

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Discussion Starter #6
Ok, I have an update on this, I have a one way check valve on the way so I still need to fix the boost leak/vac leak however I have found 2 things have made a big difference. First thing is spark plugs, changing to new NGK plugs has made a HUGE difference in power - I have a feeling the plugs were original! this has restored a huge amount of lost power and the car now boosts properly due to the fuel actually being ignited!

Secondly, I took off the throttlebody to give it a clean, it was only 2 bolts for the hose and then 4 bolts for the actual throttle body, I was expecting an idle control valve on it but it seems that this engine doesn't have one - its all controlled by the electronic throttle it would seem. I noticed that when cleaning the throttle body the plate doesn't 100% match with the opening - letting a small amount of air past for idle control. I noticed that the bottom part of the throttle body was very oily and mucky meaning that if this engine just relies on the small gap around the throttle plate then this blocking would have caused issues.

I am going to install a catch can onto the engine to avoid oil and muck being chucked into the intake hose leading to the turbo - will take a photo when I get it fitted.

One thing I am keeping an eye on is the long term fuel trims, initially the ECU was showing a long term fuel trim of around +35% which is very rich, changing the plugs out and a few initial drives and the fuel trim is around +18%, yesterday after a bit more driving it was at around 15% so it looks like the ECU is relearning the fueling. I did try and find the ECU fuse but I believe its in the engine bay buried under a fair amount of wiring - at least the fuel trim is gradually moving in the right direction.

Next on the list is to sort out an oil change and swap out the air filter, I am going to look to still run the check valve in the intake manifold as stock but collect things in the catch can, the issue I have at the moment is that there is a boost leak due to the OEM valve no long being one way - the check valve will sort this.

I think also once the fuel trims are down to a more normal level I will try again to block off the intake manifold and see if I can get it to idle by it releaning - the engine is set to a very low RPM of 650 to get into the lower emissions tax bracket, I will still try and find an idle control valve to clean but it would seem that its done via the throttle body instead.

Will keep this thread updated!
 

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Discussion Starter #7
Just nipped out again to check a few things, the car was up to temp and would normally stall out when trying to reconnect the smaller intake hose to the main breather hose (would idle okish if it was in warm up), I quickly connected up the hose (although its still broken at the broken check valve) and the car managed to idle ok even when fully up to temp.

It would seem that once I have the new check valve in place the car should be back to normal - it would seem that the issue has been tentatively fixed - for me it would seem to have been a combo of old plugs and a slightly oily and varnished throttle body - took about an hour to change/clean both on Friday so well worth it.

I will definitely be installing a catch can on this engine, although the injectors are port injectors so would clean the back of the valves, oil and muck can still get stuck to the throttlebody which is where I think the issue lies as it needs to be perfectly clean to idle properly (especially at such a low OEM idle).

Once the check valve arrives (hopefully this week), I will install that and see what the difference is - would also recover some of the lost power as well as the boost would be leaking.
 

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Quick update, still working on this, I am currently running some injector cleaner through which does seem to be improving the performance slightly, I also have a spare throttlebody to try out as well. I do also have a spare low mileage breather Y pipe on the way from another car so will see if that makes a difference.

I have also noticed that the engine temp is only getting to around 80c, its stable so I think the incorrect thermostat has been fitted - might mean that its running slightly too cool and still on its warm up cycle, I believe the temp sensor is correct though.

The car still works fine, but the MPG is a bit lower than expected at around 36mpg, need to give everything a good service as I am expecting to get mid to high 40s with this car, the long term fuel trim seems to still be a bit high which makes me think its still on its warm up cycle even though the engine is up to temp as per the thermostat.
 

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I believe I have sorted this now, but I guess time will tell, turns out that the issue was mainly around maintenance, the engine needs to be clean and properly serviced for it to be able to idle properly, main fix was a new set of plugs which improved the drivability. Next was cleaning the throttlebody which helped with smoothness. I think the thing that is now allowing it to run properly is that I have just run a can of cheap injector cleaner through the system and its made a fair bit more difference.

It would seem that the ECU does adjust the idle down via the throttle body (no idle control valve), the issue is that at very low RPMs it relies on the perfect amount of fuel, with clogged injectors at 90k miles they weren't able to properly inject, now with the injector cleaner run through the system they can so the engine can idle at the correct low 650rpm.

I still need to get the oil fully changed along with the filters but its coming together - night and day vs how I picked the car up.
 
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