My engine was shaking and rattling on shutdown which gave me a feeling of dread thinking it was DMF failure however there were no symptoms when driving even if accelerating from 800rpm in 6th gear, I decided to remove the motorised throttle valve for cleaning having read that it could cause this problem if the carbon build up prevented it from closing properly.

 

I was surprised by how clagged up it was, I thought I had left decokes behind me decades ago but it has had the emissions fix so spends too much time ingesting its exhaust gases.

 

It was purely a soot build up and there appeared to be no trace of oil in the turbo pipework, the venturi was restricted, the throttle plate elliptical instead of flat and there was a lot more crud downstream in the inlet manifold which I removed as best I could - tip, stuff a rag in the open air pipe from the intercooler to stop the crud or anything else dropping down there to be ingested later.

 

I also removed the EGR inlet boss & shroud as that too was covered in clag, the open end of the shroud faces upstream towards the throttle valve & opposing the incoming airflow which seemed odd to me, I was tempted to reverse it (it would fit in either direction) but wondered if it was for mixing purposes, the way its aimed you would think they wanted it to clag up the throttle valve.

 

What is the correct orientation of the EGR inlet boss/shroud?

 

There is no EGR valve so I deduce that the throttle valve closes to allow EGR in varying amounts, I am tempted to fit a reducing plate (I have one left over) with a metering hole drilled into it to reduce to a minimum the EGR gases, does this throw up a fault code like on my PD Octavia and if so is there a minimum hole size? Is there in fact any monitoring of the airflow upstream of the throttle valve? - There is nothing on the EGR pipe.

 

Finally the clonky shutdown seems to be resolved and the car seems much better to drive, better low revs/light throttle flexibility and more power on full throttle, it had always seemed gutless before and now it seems to have its 108hp and more, it might be a placebo effect but if the MPG improves then I can be sure.

 

A very worthwhile job for anyone with the same EGR system to tackle, mine only had 80K miles.

Edited 6 September, 20205 yr by J.R.

In this post they turned  the egr inlet shroud 180° by filing a new notch.

 

Interesting that the EGR can be disabled by connecting a spare slave throttle valve to the wiring loom leaving the original in place but non functioning.

 

I could try removing the throttle butterfly from the spindle but I think the engine shut down will be very  violent.

 

I will reverse the shroud in the first instance and then work on limiting the volume of EGR by a metering hole in  a blanking plate.

I have just had a Eureka moment, if I remove the butterfly from the throttle spindle it should have the same affect as connecting a spare throttle valve.

 

It might cause a very unruly engine shutdown though, I may give it a try.

I think you will need one of these if you want to disable the EGR.

https://www.ebay.co.uk/itm/11-EGR-AGR-Emulator-Simulator-Plate-for-VW-Audi-Skoda-Seat-2-0-TDI-CR-II-Euro-5/183869556154?hash=item2acf7ac5ba:g:OaAAAOSw-DRdHK14

The EGR should be tucked away at the back of the engine, in a rather difficult to get at location.

 

I'm fairly sure that during a regen the butterfly on the throttle valve needs to partially close, this then limits the air flow into the engine/ exhaust to keep the temperature as high as possible.

So eliminating that butterfly may give you DPF problems.

Good point, I will read up on my self study guides before playing with anything.

 

My petrol head doubts the above as the mixture would be enriched and the lambda sensor would cause the ECU to weaken it to achieve lambda 1 but even after driving diesels for close to 20 years my head wont think in diesel terms.

 

I need to read up, thanks for the warning.

My son's car, which is now the wife's car, ( Passat 2l CBAB ) had the throttle valve fail a few years ago.

While failed ( butterfly fully open ) it wouldn't do a regen, regen warning light up.

 

I looked at it & found, apart from all the black gunge around the butterfly, the electronics under the plastic cover were full of black ( electrically conductive ) engine oil.

This had run down from the EGR & entered the electronics via the butterfly spindle, you couldn't make it up.

 

I fitted a new one as he lives some way away, otherwise I would have tried just cleaning it all out with brake cleaner, took it for a run & it immediately did a regen & has been fine since.

 

My current car has nearly 200k on the clock, had the emissions update before I bought it unfortunately.

Although I didn't have any problems, thought I was probably running on borrowed time so fitted the above to be on the safe side.

 

The throttle valve on badly gunged up valves sometimes stick shut, resulting in a no start situation. ( As happened with my other son's Tiguan ).

I wonder if it "thinks" it is working i.e. butterfly removed but spindle moving & potentiometer making the right noises whether it would do a regen & whether it would be a satisfactory one, I will read up & may give it a try.

 

Failing that I have a spare EGR flange blanking plate from buying a pair when I did the Octavia, I might try that with gradually increasing hole sizes to limit the amount of EGR gases passing.

 

If ever I get back to the UK a remap is on the cards & if I go to their workshops for it they say they can undo the emissions fix FOC which would be the best thing all round, anything else is trying to polish a turd.