EGR Valve - replace or not......

[mrh]

An update....

The vacuum hose to the top of the EGR has been replaced.

I've had the EGR off and given it a good clean - and the pipe linking the exhaust manifold to the EGR valve (the top few inches were almost blocked with gunge).

We also checked the operation of the diaphragm etc as per the service manual. We applied the vacuum - the diaphragm lifted. We held the vacuum and the diaphragm stayed lifted. When we released the vacuum the diaphragm dropped.

From this we feel that the diaphragm is working fine and so the EGR should be ok. Shouldn't it?

The valve and valve seat all look ok also.

Drove 30 miles this evening after reseting the error code. All OK. 1 mile down the road on the way home and the same code has re-appeared.

I'm concerned that I may go and spend my £124+VAT from GSF and still have the problem.

Can anyone offer any advice/suggestions?

Thanks

Matthew

[rwbaldwin]

The ECU uses the drop in airflow to determine the EGR has opened. It has no way of directly measuring EGR operation/flow.

If the MAF is not working correctly, you can get this error. Check the MAF.

[mrh]

The ECU uses the drop in airflow to determine the EGR has opened. It has no way of directly measuring EGR operation/flow.

If the MAF is not working correctly, you can get this error. Check the MAF.

Thanks for the quick reply - much appreciated.

What is the best way to check the MAF?

Thanks again,

Matthew

[Supurbia]

When you replaced the hose did you have to pull it hard off the nylon hose on the bulkhead?

If so with the cover removed check the other end, i.e that lot just the other side of the derv filter, it's possible you could've damaged one or disconnected it without noticing, as you can see I'm still trying to give you cheap options, I think you did say you replaced the hose didn't you? if you've simply taped it up it won't work as the heat from the fumes melts the tape and you get a hole, and also did you use the correct hose of something that looked the same from a factor's? all this needs checking, the hose should have thread reinforcement in it, see this by looking at the end, should look like stitching, check that lot out before you do a good nights sauce in on a new part.

[mrh]

The ECU uses the drop in airflow to determine the EGR has opened. It has no way of directly measuring EGR operation/flow.

If the MAF is not working correctly, you can get this error. Check the MAF.

OK.

A quick google and I found how to get the MAF readings from VAG-COM.

Engine speed MAF (specified) MAF (actual) EGR duty cycle

TIME 790-870 230-310 210-350 40-75% TIME

Marker STAMP /min mg/str mg/str % STAMP

0.38 819 250 416.5 84.5

0.78 819 250 416.5 84.5

1.19 819 250 416.5 84.5

1.61 819 250 416.5 84.5

2.01 819 250 406.7 84.5

2.39 1323 550 392 19.9

2.79 2268 390 529.2 44.2

3.19 2373 260 607.6 75.7

Is the discrepancy between the MAF (Specified) and the MAF (actual) normal, or a sign of the cause of all my problems? (the 3rd and 4th columns)

Many thanks

Matthew

[rwbaldwin]

You need to do the test at WOT to at least 3500 rpm (through the gears).

Take a look at this

Good or Bad MAF

You should get similar values.

A quick look at your figures leads me to believe the MAF is faulty, but do the test again at WOT to be sure

HTH

[mrh]

You need to do the test at WOT to at least 3500 rpm (through the gears).

Take a look at this

Good or Bad MAF

You should get similar values.

A quick look at your figures leads me to believe the MAF is faulty, but do the test again at WOT to be sure

HTH

That's great - thanks very much.

I'll take a detour on the way home tomorrow and set vag-com logging.

I'll report back tomorrow!

Thanks again,

Matthew

[Supurbia]

If it is the MAF the car will run sluggy without turbo assistance normally, whatever you do, do not be tempted to wipe it clean or you will kill it just like that.

[mrh]

You need to do the test at WOT to at least 3500 rpm (through the gears).

Take a look at this

Good or Bad MAF

You should get similar values.

A quick look at your figures leads me to believe the MAF is faulty, but do the test again at WOT to be sure

HTH

Please see attached for the trace - still not sure what it is telling me!

Many thanks

Matthew

MAF.pdf

[mrh]

Please see attached for the trace - still not sure what it is telling me!

Many thanks

Matthew

I am now wondering if I haven't got the revs high enough to be of any use.