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1.6HDi EGS Shudder (Solved)

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Author Post
Wed Dec 03 2014, 04:53pm
Member No: #33590
Joined: Dec 24 2013
Location: Gosport, Hants
Bit of background - I bought my C4 1.6HDi EGS VTR+ 110hp '57 almost a year ago. I like fiddling with mechanics and elctronics and I consider myself an amateur vehicle engineer with some experience. I like to logically play with cars to understand how they work and improve upon them, with economy/efficency in mind.

Since I have owned the vehicle the major things completed by myself are blanking the EGR, removed the Cat and DPF, which brought some issues but I have managed some work arounds. I have also replaced the oil including removing the sump to ensure the engine clean of gunk/debris in the pan. I also removed the gauze filter in the turbo feed pipe under the impression that I would rather have dirty oil reaching the turbo than no oil at all, even though it passes through the engine oil filter first. I have also replaced the oil in the EGS hydraulics just in case this was causing issues. Originally the car was completely standard with no faults.

The car originally did suffer from shuddering but I do not remember it being too bad. First mod I did was to blank the EGR with the £3 (approx) plate which can be obtained from ebay, fitted in a couple of hours and noticed some improvement in pick up but nothing major.

Then removed the Cat first, which threw up a EML/MIL indication, presumably because the cat wasn't restricting flow prior to the DPF, producing a higher pressure across the pressure differential snesor for the DPF. If I remember correctly a disconnect of the battery sorted this issue out with no further issues.

Next to go was the DPF, again threw up an EML/MIL and depollution fault. To work around this I placed the upstream feed for the DPF differential sensor to the post DPF connection (not sure if this mattered, probably not) and disconnected the post DPF sensor to atmosphere. The intention here is that with the DPF removed, in order to see a similar pressure differential as if the DPF was still there, then the down stream connection would require to be more negative than the upstream, hence the downstream half of the sensor being vented to atmosphere. The pipe from the exhaust was blocked to ensure exhaust gases were not escaping in the engine bay.

Overtime I had a really bad stuttering, especially when cold and efficency of the engine wasn't what I had been expecting with a gain of about 2mpg over 3000 mile. The mpg could be due to a heavier right foot but found it didn't have the torque for light throttle adjustments like I wanted from previous diesels.

Next I looked at the air douser/double air meter (whatever you want to call it) located post intercooler which can mix hot (direct from turbo) and cold (from intercooler) air. So with some patience and hours of googling looking for the right picture and explanations I believe I have found what I was looking for. There are 2 valves in my unit. The 1st valve when open lets hot air direct from turbo to the inlet manifold (ideal for warming up when cold) and basically shorts out the intercooler (in electrical terms) so the air takes the route of least resistance and therefore bypasses the intercooler. This 1st valve I have left alone.

Now the second valve is of interest to me when doing my research. It is called an EGR throttle on some diagrams I have seen (google images air doser, 3rd picture). Now why is this called an EGR throttle?? I have seen butterfly valves in the induction of diesels before which are normally called anti-shudder valves. These operate by shutting off air supply when turning off engine and therefore reducing engine movement. Now in this guise it is known as an EGR throttle as I have already mentioned. This works in conjunction with the EGR valve so when the EGR opens, the EGR throttle closes slightly therefore reducing air and encouraging exhaust gases into the intake manifold. Now I believe this EGR throttle (like you have on a traditional petrol car) would reduce efficiency by introducing pumping losses, which diesels are inherently known to have a small amount of.

Now to the shuddering, I believe that when pulling away in the car the EGR should be partially open and the EGR throttle would then be partially closed, as the 2 work in conjuction with each other. Considering I have blocked the EGR valve the engine would then almost stall as the EGR throttle is partially open/closed, hence the shuddering.

With this in mind I removed the butterfly of the EGR throttle and the difference so far is night and day. It is so much smoother when pulling away and small throttle changes make a difference with the requirement for less gear changes due to some extra torque (not a world changing amount but enough). I have only completed 2 journeys so far (inc motorway) and will continue to observe and report any further findings. So far no fault lights. Removal consisted of unscrewing the butterfly off the spindle (2 screws) after the air doser was removed from the car.

To be honest I initially thought the shuddering almost felt like the ESP was kicking as if one wheel was not turning or the sensor/sensor wheel was damaged, thereby applying the brakes on one of the wheels, but now I do not believe this to be the case or if it could happen by operating in this manner.

I have done all this work myself, without un-programming any of the equipment I have listed and was completed without any major faults or headaches so far. If anyone wishes to follow what I have done I cannot guarantee it will work on their car but I am happy to aid people best I can. I do not know if there are any silent faults as I do not have a fault reader to hand and I'm too tight to take it to a garage. This may or may not help people with a juddering issue and depends on the mechanical state of their car.

Hopefully I have posted this in the correct area and at the correct level for all to understand.

2 User said Thank You to nitropixie for this Post :
 wilcovh (04 Dec 2014 : 05:04) , wesso (15 Nov 2017 : 18:23)
Thu Dec 04 2014, 02:33am

Member No: #1
Joined: Aug 07 2006
Location: Northumberland
Be interesting to hear what happens at MOT time.
Thu Dec 04 2014, 05:10am
Member No: #28268
Joined: Nov 22 2012
Location: north wales
Interesting. Especially the part of the egr throttle valve. I'm just thinking that only the removing the throttle valve, would that benefit the economy as when the egr opens this valve cannot throttle and so less exhaust is returned to the inlet.
Also it is invisible from the outside and thus nearly impossible to detect at mot.
Thu Dec 04 2014, 10:01am
Member No: #33590
Joined: Dec 24 2013
Location: Gosport, Hants
After driving to and from work this morning the car does feel better driving from standstill but I have noticed a stutter when accelerating from walking pace (in traffic), which I can only conclude is caused by the EGS system. Maybe a battery reset may help with this so further testing is required here. I do not have any fault indications at the moment but then I have only completed 35ish miles. Fuel economy still hasn't risen yet but then I am only doing short traffic journeys during busy times at present.

Admin Dave - My car recently passed an MOT last month, although the emissions part I did not fully understand as it seemed to be on the limit. With my old picasso 2.0 hdi it was well within limits. Guess that is euro 4 for you. I was thinking that without the CAT the EGT sensor is not seeing as much temperature and therefore increasing fuelling to compensate in order to keep the DPF working correctly (which is no longer there)

Wilcovh - It may benefit economy, but should provide smoother running. One problem is that once the butterfly is removed you may have to take the whole unit apart to re-attach it. The spindle is spring loaded and once the butterfly is removed it will be very difficult to rotate the spindle in order to locate the butterfly onto ithe shaft, be warned. I may remove the blank out of the EGR at some point to see if there is any difference. As my dpf and Cat have been removed there should be less pressure forcing exhaust gases into the intake manifold (with EGR valve open) although the turbo will cause some back pressure. Also the lack of EGR throttle would hopefully mean an increased pressure of clean air would also oppose exhaust gas pressure (but not by much). There would also be an increased engine wobble when the engine is turned which is noticeable, so I think I will change/modify my engine mounts soon to ensure they remain serviceable.

This has got me thinking to engine runaway, aka when a leaky turbo fuels the engine. With the egr throttle in situ it can cut air supply to the engine and stall it when turning off the key, what happens now I have removed it and this happens is the question?? Have I made the engine more likely to runaway upon turbo failure??
Thu Dec 04 2014, 12:39pm

Member No: #82
Joined: Jan 22 2007
Location: Hoylake
nitropixie wrote ...

Admin Dave - My car recently passed an MOT last month, although the emissions part I did not fully understand as it seemed to be on the limit. With my old picasso 2.0 hdi it was well within limits. Guess that is euro 4 for you. I was thinking that without the CAT the EGT sensor is not seeing as much temperature and therefore increasing fuelling to compensate in order to keep the DPF working correctly (which is no longer there)

Drivers who try to dodge the diesel car trap by having particulate filter removed will now automatically fail MOTs

You were very lucky. I appreciate the cost of maintaining the DPF system can be expensive to keep fuel consumption low. Take care, and remember you are making disclosures on a public forum.
Thu Dec 04 2014, 02:22pm
Member No: #33590
Joined: Dec 24 2013
Location: Gosport, Hants
Fair point and note taken.
Fri Dec 05 2014, 04:35am
Member No: #1731
Joined: Dec 15 2007
Location: Walsall West Midlands
BigJohnD wrote ...

nitropixie wrote ...

Admin Dave - My car recently passed an MOT last month, although the emissions part I did not fully understand as it seemed to be on the limit. With my old picasso 2.0 hdi it was well within limits. Guess that is euro 4 for you. I was thinking that without the CAT the EGT sensor is not seeing as much temperature and therefore increasing fuelling to compensate in order to keep the DPF working correctly (which is no longer there)

Drivers who try to dodge the diesel car trap by having particulate filter removed will now automatically fail MOTs

You were very lucky. I appreciate the cost of maintaining the DPF system can be expensive to keep fuel consumption low. Take care, and remember you are making disclosures on a public forum.

If everything you have done is legal in regulation terms there is the issue of an increased band for VED purposes as your car is now more polluting. As John has said, be careful what you say, a site as well known as this may be monitored by many agencies including the DVLC.
Tue Mar 03 2015, 08:54am
Member No: #33590
Joined: Dec 24 2013
Location: Gosport, Hants
More food for thought.

I have been wandering about the shuddering again, as I still get some especially during these colder months. This time I have been looking at the engine mounts. There are 3 mounts in total (as with most cars) which are located next to the top of the cam belt cover (Part No 2), above the gearbox (Part No 15) and to the bottom rear of the engine (Part No 3 & 5). Other vehicles have the third mount attached to the diff sometimes.

I will be referencing the below diagram, although not necessarily for this model of car is similar and good enough for a generic diagram. I found this image from this site on google images, therefore I hope it is ok for me to use.

On inspection of the engine bay I find I could wobble the engine slightly with both hands and a moderate amount of force, which in my eyes meant everything was ok. Whilst driving I noticed a slight knocking sound over bumps (probably suspension) but the worst bit was when pulling away and coming to halt I would feel a single thump which led me to think further about the engine mounts. Also when accelerating from cruising there was feeling of nothing then a lurch, not a smooth progressive response.

As I look at the engine, the left hand (drivers side, cambelt side) engine mount (Part No 2) looked fine, a little bit of fatigue (cracks in rubber) at the base but I could not see a mechanical reason why this would cause an issue. As the car is 8 years old and more than likely on its original mounts I placed a 4mm packing piece (plastic) on one side in order too "tighten" the mount. This was completed by removing the 4 bolts securing the mount to the chassis, bending back a tab between 2 of the bolts and lifting the top half of the clamp away, inserting packing and bolting back on. Easily completed with the correct socket.

The right hand side (passenger, gearbox) mount (Part No 15), I had bought replacement for from Euro Car parts a while ago which was the correct shape but too small and therefore not fit for purpose.
- Click Here -

The mount is not so easily changed as it sits under the battery tray (Part No 14). The battery tray (metal bit) is mounted with 6 bolts, 5 of which are easy to undo but the 6th requires access under the wheel arch behind the plastic liner. I did mine with the car on axle stands and the wheel left bolted on.

This mount was in a bad shape and an internal metal sleeve had come away from the rubber exterior causing a lot of movement. This was the worst condition mount out of all 3. My fix was to pack the sleeve into the engine mount with sikaflex 221.

- Click Here -

There are different versions of sikaflex and cannot comment on those. I have used this one in the past at work for weather proofing seals on off-shore ships and works a treat but is horrible to use. Tips: warm tube in airing cupboard prior to use in order to improve flow and ease of use, wear disposable gloves otherwise the better half will take great joy in scouring pad your hands in boiling water to get it off, only get it where you want it otherwise it will get everywhere. This stuff has really good sticking properties and sets just like rubber, which I believe is good for the job. There are other car forums which have used similar stuff for upgrading/improving/bodging their engine mounts, take a surf.

The third mount at the back of the engine is made up of 2 parts, an aluminium bracket with a large bush pressed in and is bolted to the engine (Part No 3) and then a fork with small bush that attaches between the large bush and chassis (Part No 5). Part No 3 indicated some signs of fatigue with some stress cracks. Part No 5 is made up of a solid bush and was still fit for purpose on inspection. Part No 3 mount is very difficult to remove as the bracket has the offside driveshaft passing through it, located with a bearing. This means that complete replacement would most certainly involve draining gearbox oil, pulling offside suspension apart and then fighting the driveshaft out of the gearbox. Not impossible or difficult just time consuming and messy.

Again I packed this with Sikaflex 221 in situ but with Part No 5 removed for access. This was fairly difficult to complete due to the vehicle being only on axle stands and sliding on my back under the car so I may have not completely covered it in Sikaflex, I aimed to mostly fill in the air gaps within Part 3's bush. A car lift would of made the experience much more pleasant.

After leaving the Sikflex to set over night, which is cured by exposure to moisture in the atmosphere, the difference has been positive so far. When rocking the engine by hand there is next to no movement and feels solid. Upon starting the engine there is less cranking shudder but can feel a bit more engine noise through the pedals and steering wheel but nothing that is uncomfortable. When pulling away and coming to a halt the thumps have stopped and the vehicle altogether feel more positive and less jerky. When the engine is switched off it used to shudder which I thought was down to the anti-shudder valve being removed but this has also stopped or is less noticeable anyway. The suspension does not knock as bad as what I had thought and may hold off doing the ball joints and track rod ends a little while longer, as it must have been the engine mounts causing the noise.

I did notice that the discs were in bad repair so looks like I am back outside getting my hands dirty again, Love It.

I shall report any further findings over the next week or so to see if there is an improvement to the dreaded shudder.

Sun Mar 29 2015, 08:43am
Member No: #33590
Joined: Dec 24 2013
Location: Gosport, Hants
After about 3 weeks since conducting some maintenance on the engine mounts I have noticed an improvement (reduction) in the magnitude of the shuddering but I am still noticing some.

My next thought this morning was the MAF (Mass AirFlow)sensor on the car. Using the torque app as an indication, the MAF looks as though it is functioning correctly and averages a reading of 90 units at idle and increases and decreases as it should when accelerating, decelerating and constant speed.

So the MAF is functioning, but is it giving a correct value or are there any other factors to consider which could be cause an issue. And therefore could some of the jerkiness be related to an air/fuel ratio.

Today I disconnected the MAF sensor prior to a journey to the cinema and the car almost felt like it was going to do its jerky thing but then it didn't and pulled away fairly smoothly, even driving along in a 30mph felt smoother. During the journey I spent a short time on the motorway and I floored it in 3rd gear whilst gaining speed at which point I noticed a big black cloud exiting the exhaust for a moment, not fuel related but looked more like carbon build up, from experience of Italian tuning my wife's Micra DCI as she doesn't go any faster than 40mph. Would be interesting to know where it was all stored in the engine and certainly felt sorry for the vehicle behind.

The MAF measures air into the engine and helps the ECU to workout how much fuel to inject. If the MAF is degraded or there is another factor causing an issue then the ecu could be injecting the incorrect amount of fuel causing further jerkiness. Disconnecting the MAF sensor results in the ECU flagging a fault and reverting to a fuel map without MAF, controlled more by the throttle position.

Between the MAF and turbo there is engine breather which directs harmful fumes produced in the block of the engine and burns it through the combustion process. So for instance, if the oil cap was not fitted whilst the engine was running then air could enter the intake without being measured by the MAF causing a leaner mixture. When the combustion process is taking place a condition called 'Blow by' takes place which is combustion gases getting past the piston rings in each cylinder into the oil part of the block (hence why diesel lubrication oil when it gets changed is so black). As engines get older this 'blow by' situation obviously gets worse and in turn could be reducing the efficiency of the MAF.

So what have a I proven and how to fix it. I believe there is an issue with measuring airflow into the engine and removing the MAF has shown this.

Possible solutions:-
1) Change MAF and use Torque app to see if there is any difference.
2) Leave MAF disconnected and only plug it in for MOT.
3) Plug or reduce size of engine breather hole, which could force oil out of seals due to increased crankcase pressure.
4) Fit an oil catch tank vented to atmosphere causing a mess in the engine bay and increase smell inside vehicle. This will also benefit that only clean air would enter the cylinders and not inert gas from 'blow by'.
5) Change the size of the aperture at the MAF sensor therefore causing a greater speed of airflow per air mass and therefore fooling the ecu to inject more fuel (trial and error).

At this present time I cannot evaluate the condition of the DMF and this could also be causing an issue although I am not hearing some of the sounds which have been reported by other users so fingers crossed. Looking for a possible SMF solution at present but I may have to end up doing a bespoke unit with having an EGS gearbox which could be costly and I would not fork out for.


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