Blanking EGR Valve?

[Martin Mc]

I'm trying to eliminate the most likely causes of a very sooty exhaust at idle and when warm (car not moving, all in workshop) and have read on various forums about the role played by the Exhaust Gas Recycling (EGR) valve. A number of sites suggest blanking it off, as for most driving conditions it doesn't do anything particularly significant or useful, but when clogged with carbon deposits, it can cause the fuel mix to be unnecessarily rich. EGR blanking plates appear to be readily available on eBay for most models, though I suspect it would be a case of fashioning one for a car of the 480 vintage.

Has anyone any insights into the issue? Things like consequences for MOT, ECU error codes / states resulting etc would be useful.

As a bare minimum I am planning to take the EGR off and see if it needs cleaning. Any tips on that process would also be welcome.

Cheers!

Martin

[Alan 480]

which engine, nothing on the two litre

[Martin Mc]

Hello Alan,

It's the 1.7 renault lump, 1995 vintage, with only 45000 apparently on the clock.

Cheers!

Martin

[Martin Mc]

This thing: Lettering indicates it is a Bosch unit.



Got it off, but can't really see where to go next, as there is no obvious way to look inside the beastie.

The petrol that flooded out of it appeared to be clean, and there were no obvious blockages of the type indicated to look out for..

Am a bit stumped now. The car still runs rough, and there is still soot in the exhaust during and after warming up..

What to do next - anyone had any experience of getting at the injectors and associated wiring?

Cheers!

Martin

[Jay-Kay-Em]

I'm confused!

The title says EGR valve, but the picture is that of the fuel rail pressure regulator?

The EGR valve reintroduces exhaust gasses into the inlet manifold to reduce Nox.

The fuel pressure regulator (pictured) adjusts rail pressure dependent on inlet manifold vacuum (where vacuum is equivalent to engine load).

Problems with either can make an engine run rich.

Excessive rail pressure means more fuel injected = rich.

A stuck open EGR valve reduces the amount of oxygen for combustion = rich.

Vacuum lines are the biggest downfall with the actuation of both of these components. These are easy to check.

The Haynes manual runs through some EGR checks.

My personal opinion is that it was fine when it left the factory, so nothing needs blanking off. It has a fault which needs to be correctly identified. Fuelling maps are programmed with EGR as a consideration. Remove and blank-off EGR and the fuel map may now be to lean when EGR should be engaged (between 1400 and 3150rpm).

Get it on an exhaust gas analyser and confirm its running rich. Then, run through all the normal running rich causes (blocked inlet tract or air filter, O2 sensor, stuck open injector etc..)

If its running rich enough to produce visible soot out of the exhaust, it must soot its spark plugs up in a week and conk out?!?!

Get it fixed soon because rich enough to produce soot will destroy the CAT in no time.

[Martin Mc]

Haha! Well I guess that explains the amount of fuel that spilled out!

I'm sorry for the confusion - I'm stumbling along clutching at straws I'm afraid, and the Haynes manual definitely shows the item pictured above as the EGR valve

Thanks for your comprehensive answer and very well set out advice as to how to proceed. I'm getting near to the point where I will need to leave the car with the garage and wait for the inevitable £££ to rack up which is something I've tried hard to avoid. To be honest the whole fuel / exhaust side of things is something of a mystery to me anyway, and it doesn't look like an aspect of the 480 that can be easily (or safely) tackled by the average (or under average in my case) DIY enthusiast.

On the CAT front, I think that was already shot when I bought the car, so I have budgeted for a replacement once the rich running is sorted out.

Thanks again!

Martin

[Martin Mc]

Ok, checked the Haynes manual (p129) again, where the only reference to the EGR sits, together with a picture of the EGR system (fig 4.52).

Turns out I should have gone to SpecSavers

Will resume my education at the weekend. With my glasses on this time

M