c5 egr valve

[andyx11]

Hi all I drove to Andover yesterday from Reading about 40 miles on way there the c5 hpi went like a dream coming home about 6 hours later all warning lights came up and the usual ANTI POLUSION MESAGE engine light which when I tried to put my foot down started flashing , service light and ESP/ASR WARNING MESSAGE the car wouldn't go above 3000 revs it would really badly misfire got home left it for the night started this morning still ropey but not as bad ,I changed spark plugs and coil pack even better but not right then I unplugged the EGR valve eclectic connection and had a drive no more misfire and the car seems more responsive than ever will I do any damage by disconnecting the EGR ? and if I unplug the battery will that clear the fault? thanks Andy

[GiveMeABreak]

It shouldn't do any harm - but sounds like it is blocked and could do with a clean. The EGR provides the exhaust gasses to the engine, it's almost like opening the throttle up a bit more but without producing more power or burning any more fuel. Technically you are filling the cylinder with a small mix of air / fuel and EGR gas. This reduces wasted energy and improves your fuel economy. It is of course part of the emission control system of the car.

[andyx11]

Ok Marc thanks for that what's the best way to clean it out ?

[GiveMeABreak]

Getting the EGR system checked first with the Lexia Diagnostic system should be the first step, as the Lexia will report any issues and can be used to perform actuator tests on the valve. If the internal valve is not moving properly because it is full of crud, there should be a fault code. EGR faults can be misdiagnosed though, so better to start with a visual look at the valve and a clean. This should be the cheapest option - as we know disconnecting it restores performance. These can be removed and cleaned - there are loads of general videos on this. If you send me a Private Message with your VIN number and an email address, I'll pull up any service documentation I can so you can see part location and fixings and send this to you.

New ones for the HPi are about £153, but obviously attempting to clean it first would be a cheaper solution! The Lexia will also clear the code aft afterwards.

Using a Lexia to activate and test EGR (this is on a 2.0 HDi, so may not be in the same position, but just to demonstrate)

[Hell Razor5543]

You have a slight advantage here. I have a Lexia system that does work on my C5 (04 reg), and I also live in the Reading area. If you can get hold of some EGR valve cleaner they can do a good job on the valve, but make sure to read the instructions on them (and also be aware that if you use too much spray you could cause the engine to race).

[white exec]

The EGR provides the exhaust gasses to the engine, it's almost like opening the throttle up a bit more but without producing more power or burning any more fuel. Technically you are filling the cylinder with a small mix of air / fuel and EGR gas. This reduces wasted energy and improves your fuel economy.

Sorry, but this is a complete misunderstanding of why EGR is fitted!

EGR is not an economy or power-improving device, but a means of reducing oxides of nitrogen in the exhaust. It does this by reducing the proportion of atmospheric oxygen being taken into the engine, by injecting into the inlet manifold a quantity of exhaust gas, itself oxygen-depleted.

A full explanation here:
https://en.wikipedia.org/wiki/Exhaust_gas_recirculation .

It is a primitive arrangement, which introduces gum and deposits into an otherwise clean part of the engine, and the valves themselves are prone to clogging and seizure. By disabling EGR, you would typically see a 2 mpg decrease in fuel consumption, a small improvement in available power (more complete fuel burning), but an increase in exhaust NOx. For this last reason, it cannot be legally recommended.

[GiveMeABreak]

The EGR provides the exhaust gasses to the engine, it's almost like opening the throttle up a bit more but without producing more power or burning any more fuel. Technically you are filling the cylinder with a small mix of air / fuel and EGR gas. This reduces wasted energy and improves your fuel economy.

Sorry, but this is a complete misunderstanding of why EGR is fitted!

This wasn't an attempt at explaining what an EGR valve does, I'm fully aware of how it works and that it is a form of emissions control. This is a classic case of putting too little information so others jump to conclusions - of that I am guilty, but was not attempting to write an essay here.

There are indeed savings in fuel due to the reduction in wasted energy - one of many articles out there.
http://www.tuneruniversity.com/blog/201 ... you-money/
and here:
"A non functioning or clogged EGR can lower gas mileage, raise under hood temperatures and cause you to lose horsepower as well."
http://www.mpgenhance.com/replace_egr_v ... onomy.html
and here:
"Sasaki et al. conducted experiments using EGR on direct injection gasoline engine and reported that an appropriate volume of EGR improves fuel economy and HC emissions. This phenomenon was presumably due to the intake temperature increase by EGR, which improved the flame propagation in the relatively lean region of the air–fuel mixture, which is non-uniformly distributed..."
http://www.sciencedirect.com/science/ar ... 6812000907

[white exec]

There are some extremely contentious and debatable statements in that "tuneruniversity" article, Marc.
The second article simply says that these devices clog up, and recommends cleaning.
The third article is more interesting, although it still details a trade-off between performance/economy and emissions.

[GiveMeABreak]

You have a slight advantage here. I have a Lexia system that does work on my C5 (04 reg), and I also live in the Reading area. If you can get hold of some EGR valve cleaner they can do a good job on the valve, but make sure to read the instructions on them (and also be aware that if you use too much spray you could cause the engine to race).

Andy, as James has said, there are professional cleaners you can get out there that don't require dismantling of the EGR, that you spray into the air intake (but MUST be sprayed after the air intake sensor) - here's a video showing this on a Mondeo:



Forget the fact that the guy takes the EGR valve off anyway to show you, so could of cleaned it anyway

[GiveMeABreak]

There are some extremely contentious and debatable statements in that "tuneruniversity" article, Marc.

I'm happy to leave it at 'it reduces harmful emissions and can save a modest amount of fuel'

[andyx11]

Ok lads thanks for all your suggestions but would my EGR be blocked or gummed up as my car has only done 56000 miles ?and is petrol not diesel?