EGR Problem

[graphite58]

I have a 2002 Skoda Fabia 1.4 16 valve saloon. 
For a number a weeks the EML was on and the local Skoda garage told me it was the EGR valve - they said it was stuck open.

I had to wait until the end of last month when I was paid and had a new EGR valve fitted - it was not a cheap one it was a proper Skoda one.

When I picked the car up it drove perfectly - after about 10 miles the EML came on and it was error 16786 - EGR flow excessive.

I cleared the error and the car began to run really rough - often stalling.

I ran it for about another 10 miles and the EML came back on - once the EML was on the car ran perfectly - all the stalling and rough idle had vanished.

This evening I erased the error again and the car is once again running really rough and stalling.

 

It never did this if the error was cleared before the EGR valve was replaced - it would just run normally for 10 to 15 miles and then the EML would come back on.

 

Is it likely to be a faulty EGR valve or could something else be causing the problem? I don't understand why it is running roughly until the EML comes on and then it runs O.K.

 

Obviously will take it back to the garage - but cannot do that for a few weeks due to work commitments - just wondered if it could be anything simple that I could tackle

 

Thanks 

[sepulchrave]

'16786 EGR flow excessive' fault generally indicates that there is a partial blockage or restriction in the EGR pipework rather than a problem with the valve, it's counter-intuitive but what it means is that the ECU has kept opening the valve until it cannot open any further and it is still not sensing sufficient EGR in the inlet plenum at the MAP sensor. I went through this exact issue until I bit the bullet and stripped and cleaned all the pipework and the plenum, it's a big job and tricky to do but once done will easily last the remaining lifetime of the car.

[Breezy_Pete]

12 hours ago, graphite58 said:

I don't understand why it is running roughly until the EML comes on and then it runs O.K.

 

Once the engine ECU decides there's a problem with the EGR system, it probably sticks on the EML then stops trying to use the EGR.

 

When you say 'local Skoda garage' do you mean a dealership, or an independent?

 

Do you do a lot of short journeys?  If so, try taking it for a blast up and down the motorway for 30 or 40 miles and see if there's any improvement.

[graphite58]

The garage used to be a Skoda dealer until Skoda decided they only wanted the posh large dealerships - but they were dealers from the early eighties until about 2008 - since then have been Skoda specialists 

The car mostly does short journeys in the week - but does do longer ones at the weekend. The EML first came back on when doing 70 on the local bypass 

Some people have said there is a hose linked to the EGR that can leak - do you think this could be so?

 

Thanks

[rum4mo]

Or the EGR valve pipe’s port in the TB area is chocked. Though if so, why would a Skoda specialist miss that initially and just slap a new expensive EGR valve on?

[Breezy_Pete]

3 hours ago, graphite58 said:

The car mostly does short journeys in the week - but does do longer ones at the weekend

Try giving it some exercise at higher revs than usual this weekend on one of these longer journeys. Stay in a gear lower than seems comfortable, keeping the revs up at 4000+ for a while (ten minutes plus? whatever traffic or cabin noise levels permits). You'll probably have the EML on before this.

 The reasoning I'm working on is this ; if one or both cats are sooted up (most likely the main one under your feet), the exhaust back-pressure will be higher than modelled. For a given/mapped EGR opening percentage, this will cause greater flow through the valve, through the steel tube, to the inlet manifold. Excessive flow. Driving like a nutter for a bit should raise exhaust gas temperatures and flow rate, and may torch some soot out of the cats.

 

 

[sepulchrave]

On 14/06/2018 at 18:14, rum4mo said:

Or the EGR valve pipe’s port in the TB area is chocked. Though if so, why would a Skoda specialist miss that initially and just slap a new expensive EGR valve on?

 

It's almost like they're only in it for the money!

 

Joking aside, they're all fitters now, unless a fault can be solved by swapping bits then they really don't care, they'll just keep swapping bits until the either the problem or the customer goes away.

 

Cleaning out all the pipework and plenum are pretty essential to solving this problem, I know this by experience, not by reasoning alone.

[2ndskoda]

They have done the job to CLEAR the issue. They have charged you (possibly?) for parts that may have done a further turn of service. This has not cured the problem - take it back without delay and get THEM to do the job that you paid a lot of money for fully and correctly.

As a brand, Skoda do have their faults - the biggest being the people who work on them. The level of incompetence is evident throughout the skoda dealership.

As sepulchrave says - they need to abandon the plug in diagnoser, and work through the problem in a structured experienced way.