# XTrail in LIMP mode



## digiman100 (Feb 10, 2009)

Hi all, I have only had my 55 xtrail for a couple of months and have just had a turbo failure, its only 3 years old and only done 17000 miles. Since the new turbo was fitted the vehicle now goes into limp mode (I'm assuming) as soon as I get up to around 3000 revs in any gear. Can anyone suggest anything please. Thanks


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## aussietrail (Sep 24, 2004)

Since a new turbo was fitted, they should have replaced your EGR valve as well, if not replaced your new turbo won't last long and will go into limp mode because of the closed EGR valve.

Here is the detailed explanation:

The EGR valve should open to allow carbon dioxide (which acts as a cooling gas) into the combustion chambers when the engine is under load (>30% boost). This allows the combustion chamber temperature to drop and thus the temperature of the exhaust gases. If it sticks in the closed position the exhaust gas temperature will rise causing a) the turbo bearings to fail and b) engine oil into the induction system. This can cause the engine to run on its crankcase oil until it is either stalled or goes bang. Problems with EGR valves are often the cause of rough running when the valve is stuck in the open position as well. In several cases turbos have blown but the EGR valve has not been replaced. Inevitably the new turbo unit will not last long.


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## The Mad Hat Man (Oct 3, 2006)

Interesting reply Aussie. I know of several peeps that block off the EGR to stop all the exhaust crud - oil and coke, blocking up the inlet manifold. They say the car runs a lot better for it.

Not quite sure how Exhaust Gases can cool the combustion chamber.


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## aussietrail (Sep 24, 2004)

The Mad Hat Man said:


> Not quite sure how Exhaust Gases can cool the combustion chamber.


Read-up on the carbon dioxide HERE and see the term "dry ice" which is what it's called.


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## The Mad Hat Man (Oct 3, 2006)

yu are pulling my plonker - aint ya, Aussie?
I am familiar with Dry ice - or liquified CO2 - but you arent seriously telling me that X-T exhaust gases put out liquified CO2?
We are talking aboout _*Exhaust Gas*_ Recirculation here - its gotta be at 600deg C at least - a doozil compusts because of the heat and compression in the cylinder - the only reason that you want _any _cooling ( and the reason for a Turbo Intercooler) is to cool the inlet gases so that they are more compressed and you therefore get more air in the cylinder. 

I have found this,

"The factory fitted exhaust gas recirculation system has been applied to all modern diesel and petrol engines for some years. The basic principal behind the factory part is to allow some of the exhaust gasses to enter into the inlet system, essentially helping to control the emission out put of the vehicle. However, this is not necessary as diesels are not measured on CO2 emission out put, but particulate (soot). There are two main draw backs from having this on your car. One, is that by allowing hot exhaust gas to pass back in to your inlet system you lower the effective combustion achieved, as an engine will always combust better on cold dense air (see Allard Intercoolers). Secondly, the soot from EGR mixes with the oil vapor produced by the turbo and forms a paste which sticks to the inlet manifold and ports and reduces the flow, in effect causing the engine to strangle itself."

In other words, the best thing you can do is blank the damn thing off. In fact - that might be the problem with the OP's motor. Take the EGR valve apart and see what state it is in.


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## aussietrail (Sep 24, 2004)

I am saying that carbon dioxide is a cooling agent and this has been clearly described in its defitnion. The EGR valve has been there for a reason, otherwise the manufacturer wouldn't have bothered including it in the design of the diesel engine. The petrol xtail doesn't have this EGR valve.

Here is some more info about the EGR:



> EGR Theory. EGR serves one purpose and one purpose only. That purpose is to reduce Oxides of Nitrogen (NOx). Undernormal combustion, Nitrogen(N2)Oxygen (O2) in the air and Hydrocarbons (HC) in the fuel combind into water(H2O) Carbon dioxide (CO2) and the Nitrogen remains unchanged. Under very hot combustion temperatures, the Nitrogen reacts with the other two byproducts and forms Nitrogen oxide (NO). After being released into the atmosphere, it picks up another Oxygen and becomes Nitrogen dioxide (NO2). In the presence of sunlight,
> it combines with other compounds like Hydrocarbons and forms Smog. Since exhaust gas is inert (very stable) it doesn’t burn again. So by being introduced into
> the combustion chamber, it will lower combustion chamber temps enough so that
> the Nitrogen doesn’t react with the other compounds and is passed unchanged out
> ...





> How EGR systems work The EGR valve recirculates exhaust into the intake stream. Exhaust gases have already combusted, so they do not burn again when they are recirculated. These gases displace some of the normal intake charge. This chemically slows and cools the combustion process by several hundred degrees, thus reducing NOx formation.
> 
> The design challenge The EGR system of today must precisely control the flow of recirculated exhaust. Too much flow will retard engine performance and cause a hesitation on acceleration. Too little flow will increase NOx and cause engine ping. A well-designed system will actually increase engine performance and economy. Why? As the combustion chamber temperature is reduced, engine detonation potential is also reduced. This factor enabled the software engineers to write a more aggressive timing advance curve into the spark timing program. If the EGR valve is not flowing, onboard diagnostics (OBD) systems will set a code and the power control module (PCM) will use a backup timing curve that has less advance to prevent engine ping. Less timing advance means less performance and economy.





> the E.G.R. valve is a emission control device that takes exhaust gases and re-burns them, this has an effect on cylinder combustion temp. it actually cooles it. Some vehicles with E.G.R. disabled could encounter a spark knock (ping) on light load, this is not a good thing. Most pre 2002 vehicles you can get away without E.G.R. and have no spark knock. There are a lot of variables to this such as compression ratio, engine carbon build up and air temp. Then it gets real complicated when the knock sensor picks up the pinging and plays games with the timming.


In any case, your car won't pass the emmission test if you have the EGR valve removed and that is the main reason it is there, to control emissions.


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## The Mad Hat Man (Oct 3, 2006)

aussietrail said:


> I am saying that carbon dioxide is a cooling agent and this has been clearly described in its defitnion. The EGR valve has been there for a reason, otherwise the manufacturer wouldn't have bothered including it in the design of the diesel engine. The petrol xtail doesn't have this EGR valve.
> 
> Here is some more info about the EGR:
> 
> In any case, your car won't pass the emmission test if you have the EGR valve removed and that is the main reason it is there, to control emissions.


Now I know you are taking the Mick! 

Although I read the enclosed with interest (and a convincing arguement) you cannot be baseing your aurguement on "its there for a reason, else the manuf would not have done it" - i mean - like the faulty turbo design, the loose screw in the fuel system, the handbrake design, etc. Not all the manuf does is necessarily for the best. It is also carried out within the Nissan design - as this link shows. It seems to be common practice in the 240 crowd...

I (obviously) am not familiar with the Aussie emissions system, but I do know that many cars in the UK remove the EGR with no emission problems and find the car runs better than before, primarily because of the removal of al the crud that fouls everything.
here is a link to Ebay, showing EGR blanking plates - you can see that this is carried out on Pajero/Ford/Vauxhall/VW/Mitsubishi, as well as the Landrover that I am more familiar with. I did look on Ebay.au but only found "international sellers" - in fact, UK suppliers, so maybe this is a difference between UK and AUS laws and/or emission control.


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## aussietrail (Sep 24, 2004)

The Mad Hat Man said:


> so maybe this is a difference between UK and AUS laws and/or emission control.


If you haven't done so already, I strongly recommend that you familiarize yourself with the emission laws (international emission regulations that is) which are based on the EURO emission control laws and which came from Europe and followed by the rest of the world, including Australia.

Check EURO4 and see what is says and I doubt that you will find UK not following these laws.

If still in doubt, get in touch with your local road traffic authority and ask about removing an emission control device from your car and see what they say. Not everything sold on eBay is legal, especially when it comes to emission control devices like the EGR valve or the catalytic converter.

And yes, in this case in particular I am indeed basing my argument that Nissan and other car manufacturers put the EGR valve there for a very good reason and that is to control emissions. It's exactly the same argument used by those who decide to run the car catless (i.e. remove the cat converter from the exhaust set-up) and I don;t support such illegal modifications, not because am with GreenPeace but because it is bad for the environment and against the law!


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## The Mad Hat Man (Oct 3, 2006)

must be something different in the way the law is interpreted in the UK.

I would suggest that it is the norm, for those into "tinkering" with their cars in the UK. I know of no-one that has been prosecuted for removal of either a cat or the egr. I also know that most, if not all, of those that I know have removed the egr have sailed through the emissions test at the annual MOT and noticed an improvement in the running of their engines.
Maybe we will have to agree to disagree on this one?


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## aussietrail (Sep 24, 2004)

The Mad Hat Man said:


> noticed an improvement in the running of their engines.


Removing an emission control device like the EGR and Cat Converter will no doubt free-up HP and anyone would notice an improvement in the way the engine is running, these components are restrictive ones within the exhaust set-up, but that comes at a great risk and cost to the environment and it is deemed illegal, so most if not all who do this type of modifications either put these components back before the annual check-up or pray that they never get caught on the road which will result in their cars being defected for a very long time.


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## TKH (May 19, 2007)

... and the QR25DE has no EGR valve


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## The Mad Hat Man (Oct 3, 2006)

Neither does the QR20DE, but I am not sure what that has to do with this fred?


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## aussietrail (Sep 24, 2004)

TKH said:


> ... and the QR25DE has no EGR valve


Correct, but it has 2 catalytic converters and 2 O2 sensors to comply with the latest EURO4 emission standards.


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