Troubleshooting limp mode: "Control difference - intermittent"

[defever]

Good morning B5 drivers,

I'm starting to experience limp mode during heavy load. It doesn't affect usual daily driving. When the limp mode kicks in, it can be re-set by switching off / on the ignition. It has only come on whist driving on motorway with passengers or when the car is loaded heavily and hits above 2700rpm on 4th or 5th gear. So it's not as sever as other cases I have been reading so far on the internet. I can live with it, but I would like to get it sorted sooner than later when the symptom becomes more severe and frequent.

Reading lots of information online, I learned that what I thought was a random fault code on VCDS Lite was in fact linked to the limp mode. I have the following code:

00575 - Intake Manifold (http://shop.ebay.co.uk/?_nkw=intake+manifold) Pressure
17-00 - Control Difference - Intermittent

Thanks to Doctle Odd, looking at Ross-Tech website (00575 - Ross-Tech Wiki (http://wiki.ross-tech.com/wiki/index.php/00575)) the possible causes and solutions are:

Possible Causes


Solenoid Valve for Boost Pressure Control (N75) defective
Hoses incorrect connected, disconnected, blocked or leaking
In 1Z/AHU engines, stuck/rusted wastegate or actuator.


Possible Solutions


Check Solenoid Valve for Boost Pressure Control (N75)
Check Hoses
In 1Z/AHU engines, clean rust scale off wastegate/actuator to allow lever to move.


It looks like the first line of troubleshooting is to check the hoses and N75. So, my questions are:



Might as well replace all hoses involved with turbo; which hoses should I replace (the black/ white patch fabric flexible hoses and anything else?) and where can I source the replacement?
I noticed that the black plastic sphere that's attached behind N75 is very loose to touch; is this normal? What is this called and how do I go about replacing it if faulty?
I could find the top of turbo from the bonnet view, but I cannot see the actuator lever from the top; where is the lever and how can I access it to assess its passive movement?


This is not my car, but I found a good picture of the area online:

27726

I hope that the wise people of the forum can help me guide to the right direction with troubleshooting the limp mode. I live in East Sussex and if anyone is nearby I would be very thankful for your time to teach me a little about turbo in return of nice chilled bottles of (Belgian) beer!

Thanks very much and happy motoring!

[defever]

Just a humble bump up to the top...

Following up on my questions:




Might as well replace all hoses involved with turbo; which hoses should I replace (the black/ white patch fabric flexible hoses and anything else?) and where can I source the replacement?



I've seen some yellow silicone replacement vacuum hoses in American forum and YouTube videos but can't really find something similar here in the UK. Should the hose be specific for car or can I go to B&Q and get any "silicone" or "vaccum" hose?




I noticed that the black plastic sphere that's attached behind N75 is very loose to touch; is this normal? What is this called and how do I go about replacing it if faulty?



I found out that this is a vacuum reservoir / damper (038129807). Is it normal to be loosely attached to the bracket that holds N75?

Also, as a side note, I've come across "engine decarbonisation with tap water" tip on YouTube; I might do this while I am at it, though I realise this will not touch the limp mode problem I have.

Any advice or thoughts will be greatly appreciated. Thanks very much!

[Doctle Odd]

Just a humble bump up to the top...

Following up on my questions:



I've seen some yellow silicone replacement vacuum hoses in American forum and YouTube videos but can't really find something similar here in the UK. Should the hose be specific for car or can I go to B&Q and get any "silicone" or "vaccum" hose?



I found out that this is a vacuum reservoir / damper (038129807). Is it normal to be loosely attached to the bracket that holds N75?

Also, as a side note, I've come across "engine decarbonisation with tap water" tip on YouTube; I might do this while I am at it, though I realise this will not touch the limp mode problem I have.

Any advice or thoughts will be greatly appreciated. Thanks very much!

Do NOT de-carbonise with water there's a strong chance you will hydro-lock the engine essentially ending it's life. You can buy the 4 and 6 mm vacuum hose by the metre and just cut to size. What's your engine code?

[Rob69]

Your heading along the right lines in your troubleshooting, probably easiest and cheapest is to replace hoses, black sphere is a vacuum accumulator to prevent sudden vacuum loss in the system when something like N75 demands a vacuum or your brake servo demands vacuum and the tandem pump is just ticking over. It shouldn't be rattling round loose, get vacuum hose from lots of places and here:
Hoses & Fittings, Hoses, Pipes & Hose Connectors | GSF Car Parts (http://www.gsfcarparts.com/accessories-consumables/consumables/hoses-fittings?cat=840)

Don't do the water decarb - water turning to steam in the combustion chamber does technically remove carbon in the longer term, but so does a good hot drive. What the youtube guy is doing is short term and more likely on your car to damage turbo compressor wheel or seals. It won't touch the carbon build up in the inlet manifold or inlet ports built up from the breather vapours and EGR, If you remove the manifold to clean it you'll see how much effort and solvent is required. A few minutes of water won't touch it.
Other thing is, if it does remove combustion chamber and exhaust port carbon, it then has to go through the turbo turbine and into your cat converter, probably gumming up your VNT even more.

[Doctle Odd]

On those old engines you can usually safely block the EGR without putting on a CEL. You can buy blanking plates etc or, use a plastic bb from a child's air pistol, remove the hose,attach it to the EGR with a little blob of grease and slide the hose over it and put a small fuel line jubilee over it. You can remove the inlet manifold and clean it with brake cleaner and your mother-in-laws toothbrush

[defever]

Thanks very much both!

So, NO WATER DECARBONASATION then! I'm glad I mentioned that... I've also heard of using Mr. Muscle Oven Cleaner for cleaning the turbo vanes (either the turbo in situ or turbo dismantled), but I guess this is also to avoid?? I guess the best way to clean the turbo is to dismantle it and scrub it by hand and re-assemble. I doubt I can do this myself; but there are other measures I can eliminate before getting into that.

Thanks very much Rob69 for the link on vacuum hoses, I will try to get about 5m of the silicone hoses. I thought the inner diameter of the hoses required are 3mm, based on lots of forum posts; should I get 4mm and 6mm instead? And how long for each? I found the diagram of the vacuum system for AFN engine, but it doesn't say the diameter of the hoses:

27790

I wonder if the vacuum reservoir is the leaking culprit. I will have a look at the whole system and hoses to see if I can replace the hoses myself without breaking anything.

The more I read up about it, the more I understand these parts of the car. I realised that the vacuum hoses and N75 need to be replaced at some point. And similarly, the tubo needs a good clean at least once in its lifetime (regardless of regular oil change and maintenance)?

Also, thanks very much for mentionning about Exhaust Gas Recirculation; I learned a new thing today. Doctle, if you say that I can block the EGR without getting Check Engine Light, then the EGR isn't a neccessary component of the engine?

Thanks both once again and I hope this helps other fellow drivers. This forum is very useful to look after my 16yo car!

[Doctle Odd]

The EGR system came from the same stable as 545g of butter and 568 ml of milk. On a more modern vehicle with more sensors it will flash the CEL. As you have an AFN change the vacuum hoses as needed. You can get by without the vacuum reservoir if it's holed. Zollaf the lexicographer told me about a product for cleaning turbos it's not available in Ireland and I've since forgotten what it's called. So check/replace the vacuum pipes, do a full scan before you delete the codes. If it's still going into limp mode check the N75 is working, it's a cheap part and easily changed.

[green A8]

The name Innotec(H?) rings a bell for the miracle turbo cleaner. BUT, there is no known subistute for whipping the turbo off that engine and cleaning it properly. Dead easy to remove the turbo on an AFN engine. The problem with all these turbo cleaners is that you're working blind and have no way of knowing how much carbon has been removed and how much is left to gum things up all over again very soon after you finish 'cleaning' the turbo.

[Doctle Odd]

The name Innotec(H?) rings a bell for the miracle turbo cleaner. BUT, there is no known subistute for whipping the turbo off that engine and cleaning it properly. Dead easy to remove the turbo on an AFN engine. The problem with all these turbo cleaners is that you're working blind and have no way of knowing how much carbon has been removed and how much is left to gum things up all over again very soon after you finish 'cleaning' the turbo.

I think it's some type of oil, Zollaf, being Zollaf would remove the turbo and so it right

[PaulF2.5TDi]

The turbo vanes are probably stuck.

un-sticking-your-tdi-vnt-turbo-vanes.html (http://www.audi-sport.net/vb/a4-s4-forum-b5-chassis/107121-un-sticking-your-tdi-vnt-turbo-vanes.html) may help.

[defever]

Thanks very much everyone!

I've read lots of testimony on Innotec and Mr. Muscle technique. But there are two schools of thoughts: 1) lots of positive feedback on short-term effect but nothing much on the long term impact of using foam solution in situ (or any report of disastrus result from using either foams). 2) scepticism over how much of carbon is actually cleared (or dislodged in lump risking more damage in cat or on the vanes) compared to good old "dismantle and mechanically clean the vanes" method.

I think I would go with taking out the turbo. I had a good look in the engine bay yesterday evening and it looks like an easy access to the tubo by removing the intake pipes to the air filter and to the engine to clear the space.

Ordered 6m of 3mm ID silicone tube for replacing the OEM hoses and I will have a try on the weekend. I'm looking online for N75 replacement and it seems that the part number (pressure converter 1H0906627) is very similar to N18 (1H0906627 A); some German car parts wesbite use the terms N75 and N18 for the part number interchangeably. Are they exactly identical?

[Doctle Odd]

N75 is for turbo N18 for EGR they look similar, buy from TPS or a specialist VAG factor or genuine

[defever]

An update: some observations, replacement and more questions!

An observation from the weekend; First I cleared the fault code (as per title) before a 150+mile journey on motorway / A-route on my own. I came back with some IKEA flat packs. I consciously worked the turbo as much as I can with rapid acceleration and high rev driving whenever safe to do so. I can feel the pull on hard acceleration, but I wonder if it can go harder if the turbo is faultless (or I'm just overly aware of the situation). No limp mode whatsoever, and there was no fault code when I scanned it upon returning home. So, I know it's not that severe and I can live with it. This changes, however, when I have passengers plus load.

The silicone hose came today so I tackled on replacing the old hose. I managed to do the hoses around the turbo:

27831

As Doctle mentioned, some hoses were thicker than the other, but the 3mm ID silicone hoses managed to fit okay. On the pressure converter it was bit difficult to get the silicone hose all the way in, but they are halfway in and because the system is in vacuum (instead of pressured), I assume that the risk of the hoses popping out would be less?

One of the old hoses I replaced had the middle section as plastic tubing (seen on the scuttle below), I replaced the whole length with silicone. I'm assuming that's a better alternative rather than just replacing the fabric hose sections?:

27832

Also, I am bit confused on which one is N18 / N75 and which one should go where (by the turbo or at the rear of the engine) so I took a picture of the pressure converter that was by the turbo with the vacuum reservoir:

27833

The converter's code is 1H0906627 A (with white head), which I know is N18. The picture I posted on the opening post had black head on the exact place. So, my question is; should the converter by the turbo be N18 (white head) or N75 (black head)? Or should I suspect that, at some point prior to my ownership, someone swapped the converters between turbo and EGR on my car? I know that N57 and N18 can be used interchangeably, but I also know that N18 cannot provide as much vacuum as N75, which the turbo actuator requires. Clarification on this would be very helpful and I will swap them (or buy an OEM replacement) tomorrow if needed.

While I had the intake pipes out to get to the hoses, I located the actuator rod so I checked the movement for the first time. It was quite hard to get my fingers on the rod but there was hardly any move. It didn't feel rock solid but it didn't give that much movement either, maybe 2-3mm. I tried to exercise it up and down for a min or so, but no improvement. So I think I will have to get the turbo out eventually for a good clean. Should the rod move a lot more than 2-3mm?

The worry I had with the vacuum reservoir was a simple loose screw so I tightened it and it's secured. That's done!

I will try to do rest of the hose (mainly at the rear end of the engine, which I assume for EGR) tomorrow evening and hopefully I can try out the turbo on full load soon and see how it behaves. Or, should I delete the EGR completely? That's another can of worms isn't it...

Good night and I look forward to your comments tomorrow!

[Doctle Odd]

N75 works the turbo and on your car should be bolted to the front of the engine, the N18 works the EGR and is on the bulkhead

[Rob69]

Check out youtube videos to see how far the actuator should move. The return spring is strong so not surprised you couldnt move it much with your fingers. A vacuum pump would confirm operation if you really want to see it move, Sealey vacuum and brake tester 30 quid on amazon! Not an endorsement just fyi.
Cheers

[defever]

Good morning and CORRECTION!

I thought N75 has black head and the code 1H0906627... No! I was wrong: N75 has white head and the code is 1H0906627 A. So that valve on the image on my previous post is in fact N75 and is in the right place! Thanks Doctle for clarifying the N75/N18 confusion (and I'm sorry for making you repeat what you've already told me...!)

I will finish the hose replacement and I have a camping weekend in New Forest so I can check the code before / after the journey to see if it spits out any fault code and if it goes on limp mode!

Thanks Rob 69 for the actuator tip! I did suspect the actuator might have a spring or something mechanical inside it that would prevent passive movement, as I felt it was soft on the end movement and wasn't rock solid. I think the turbo might have to come out to clean so I will check the actuator when I do this (probably in the summer...).

[31satara]

I've just successfully used the oven cleaner technique on my AFN. The actuator does now more further and smoother than it did. I can move it a bit by mouth sucking on the tube, however I found the easiest way was to get a small/medium screwdriver 'under the nut' on the actuator and lever upwards, pivoting on the turbo body (inlet side). The spring is quite strong, but once you have everything in place and lined up you can work it up and down quite easily.

[defever]

Update no2:

27858

All hoses and plastic semi-flexible hoses replaced with silicone hoses! Because I only ordered 3mm ID hose, it was quite difficult to get it on some of the bigger nipples (eg. EGR valve), but I think I did everything correctly.

Checked with VCDS first and no fault code on engine module. Went around for a 20min 3000+prm blasts on dual carriage way and, I'm sure it's more of placebo effect, it felt that the turbo was more noticeable. It did eventually kick into limp mode but I really had to push it hard and the turbo returned with ignition reset. Again, more of a placebo effect but I think the turbo maintained its function longer than before hose replacement. After I cam back home, I checked the code and the fault code is still the same: "Control difference - Intermittent".

So, the next stage of trouble shooting is to replace N57. The cheapest OEM (Pierburg) I can find is £67 on eBay. There are cheaper converters but I don't trust the quality.

Thanks all once again for your help and advice. I am learning so much about turbo, EGR and general observation about engine from this!

Good night and good luck.

[31satara]

From what I've read the N75 is pretty reliable. If after swapping hoses it's a bit better I'd suggest you spend a couple of hours with oven cleaner before you spend £67! The N75 must be working pretty well if you are now struggling to get it to go into limp mode. (Rather that hard accelerations in lower gears it's more likely to go into limp mode in a higher gear pulling up an incline after a couple of seconds if the vanes are not functioning correctly).

[defever]

Good morning and thanks 31satara for your suggestion, I'm swaying towards the Mr. Muscle trick... but I'm going to make sure that's the right thing for my issue first.

I started thinking, maybe some of the hoses are not connected correctly; I replaced one by one so the hoses are as they were prior to replacement. But what if it wasn't correct in the first place? I doubt they are wrong but I will double check this tonight. Also, I noticed that there's a hose going between ECU and some sort of air way (doesn't look like air intake filter box). I will open the ECU box to try to find this:

27861
My limp mode isn't severe. It only kicked in twice unexpectedly with full load and going up that long incline on A23/M23 to London. When I'm on my own I have to drive at high rpm and have to really push the car to its limit. I never ever go above 2500rpm in any gear and I had to go well beyond that to get into limp mode. So, I can live with it. But I’ve come this far with troubleshooting and learning about it so I’m keen investigate further into the turbo and actuator.

As Rob69 suggested, I might get a hand vacuum pump to test the actuator with turbo in situ to see the actuator movement. If the rod moves massively, then I can assume that the vanes aren’t impaired with carbon deposit (then I’ll get a new N75 to replace, as it’s likely to be a pump issue). If it hardly moves, then I can assume the turbo needs a clean.

Then the next question: Take the turbo out and clean manually (how do you clean it? What chemical? grind the carbon with Dremel?) or in situ using Mr. Muscle or Innotec.

I found this video on Innotec turbo cleaner:


https://www.youtube.com/watch?v=Z7k5yE1FAJs

It's very impressive. I wouldn't want all that sluge to go anywhere else in my car, but it looks like the chemical is injected through the exhaust end of the turbo with a cardboard gasket so I'm assuming all the gunk is then dripped on to the ground without going through the exhaust system as it would with Mr muscle trick.

SO! Innotec or Mr Muscle testemonials, anyone?! I read alot about their instant improvement on turbo performance but I'm keen to hear the long term effect of either method!

PS. I realise this thread has become long, 90% of it being posted by me. All I want to do is to learn... Sorry and thank you!

[PaulF2.5TDi]

I've used Mr Muscle on my 2.5 - worked great.
60,000 miles later and I'm looking to do it again

See 31Satara's post.

Try to move the actuator rod by hand/screwdriver until it hits the screw stop.

If you cant move it to the stop it's carboned up.
Mr Muscle is a foam Sodium Hydroxide-based cleaner that is designed to loosen carbon.

Squirt it in the hot side of the Turbo, leave for a while then move the rod.
Keep doing this until it is free to move to the stop.
Then do it again and leave 30 mins or so. Put all back together and take it for a run.

[defever]

Thank you PaulF2.5TDi

After reading further testimonials on Mr Muscle and Innotec, the consensus is split completely between “for chemical clean in situ” and “for removal and mechanical clean”.

I think, for the sake of learning and getting it right, I will try to take the turbo out and clean the vanes. I found this “how to” manual on AFN turbo:

4-cylinder Diesel Direct Injection Engine (TDI), Mechanics (http://workshop-manuals.com/audi/a4_mk1/power_unit/4-cylinder_diesel_direct_injection_engine_%28tdi%29_ mechanics/exhaust_turbocharger_g-charger/charge_air_system_with_turbocharger/removing_and_installing_turbocharger_engine_codes_ afn_ahh/)

So, I can see that the easier things I need to disconnect are a) intake pipe (and possibly air intake filter box for access), b) oil feed in / out lines and c) the catalyst. I didn’t see the turbo bracket from the top view of the engine bay but assuming there’s one at the bottom, that looks straight forward, too. Now the exhaust manifold; is it easier / safer to take the manifold still attached to the turbo, or can I disconnect at manifold / turbo junction?

27868

Are there anything else I need to be aware of?

Is this suitable for someone who just done a hose replacement, can do oil change and recently replaced thermostat and bled coolant properly?

I will get a hand vacuum pump in the meantime as it looks like a good investment for exercising the actuator and maybe brake bleed in the future.

Thanks everyone once again for your input!

[Doctle Odd]

The 3 bolts holding the turbo in place are different you'll need a socket like this 27869

[defever]

Is it Spline screw?

I'm glad I asked before doing anything. Thanks very much for the warning, Doctle.

That's the screw from the exhaust manifold is it? M8 x 46mm 12 point heald bolt (028145800) is what I see on the catalogue:

27870

I can't seem to find a socket for it online (lots of bits but not socket).

It might be an insitu chemical clean then... bolts to the catalyst is hex so at least I can remove the cat and do chemical clean in situ.

[Cavanmick]

The picture is just a 12 point hex bolt, a normal 12 point socket will open it.

[defever]

Thanks cavanmick!

Actually, the spanner set I have has 12 point ring ends! If the spanner can access all three bolts.

[Cavanmick]

Yeh 12 point spanner will do it alright buddy, any I have taken off to clean I have split the turbo and left the exhaust side on the manifold, there is a clamp around the middle of the turbo that holds the two parts together, there is a tiny roll pin that sticks out of the exhaust side that locates it going back together.

[green A8]

Congratulations on doing the work on the car yourself and even taking photos! I can't multi task like that!

I'll once again bore you by singing my 'never ever buy anything off on line auction sites' song. UNLESS they're known brands or OEM. So having bored you with that.............

I can't help but notice that the chap in the video you've posted is working in the turbo with it off the car. That's the way to do it. I have tried a couple of times to clean the turbo 'in situ' but the problem I have is you're working blind. Both the cars I treated returned with the same problem within six months. At this point I took the turbos off both vehicles and did the job properly, on the bench. Neither car has had any further problem since. (with the turbo anyway) It really isn't a hard job to remove clean and replace the turbo on these four cylinder engines. If you want a challenge, to test your DIY skills try doing the same job on some of VW Audi's V series engines.

[Doctle Odd]

Taking the inner bolt off to remove the turbo and leave the manifold in situ, you really need a socket

[defever]

Okay, another update!

While I'm learning all about this, I thought I'd clean the MAF with conductive cleaner:

27874

Wow. The dirt that dripped from the inside... I know that MAF was replaced at some point by one of the previous owner but I was amazed how dirty the cleaner dripped out. Waited to dry and put it back in.

I had another look at the turbo: The intake pipe at the turbo wasn't tight fit so I took it out and had a gander at inside:

27875

It looks clean to me? With bit of oil present, which I expect from oil feed working. The shaft was solid and no give or play, which is assuring.

But I noticed that the tube underneath the turbo was quite dirty and oily:

27877

27876

This is something to investigate further isn't it. I haven't had the chance to look the turbo from under so I should investigate further when I have the time.

[defever]

Also, as 31satara and PaulF2.5TDi suggested, I wedged a screw under the actuator rod to exercise it. It was a bit difficult to understand what they meant but I got it eventually:

27879

27880

The actuator moved all the way to the stopper at the top. I exercised it for couple of minutes and it went up and down full range. I'm not too sure if the movement was smooth or not.

So, I thought I'd take the two nuts at the base of the actuator to free it from the heat shield. I did it and I moved the actuator and the vanes managed to move full range as well....

I think this means that the vanes aren't totally sticking; maybe not smooth but it moves full range. So that leaves the culprit of my limp mode to: a) faulty N75, b) faulty actuator, c) maybe I didn't put things back in securely yesterday.

I ordered the hand vacuum pump today so I will test the actuator next week and hopefully that can tell me whether N75 or the actuator (or both?) is faulty.

I also bought Mr Muscle in anticipation of removing the turbo and having a clean... I got this far so might as well have a go on removing the turbo, investigate that dirt / oil leak and clean the vanes!

Thanks everyone for your advice, I wouldn't have been able to do all this without this forum!

One last thing: What do you mean by the inner bolt, Doctle?


Taking the inner bolt off to remove the turbo and leave the manifold in situ, you really need a socket

[31satara]

Yes that's exactly what I did to move the actuator. It was smoother after the oven cleaner treatment. There was a clear stop at the end of the travel up, and then the spring returned it smoothly. Not sure how much it moved - maybe 30ish mm?

[Doctle Odd]

The turbo is triangular where it mounts to the manifold using 3 bolts, one of them is recessed and you can only get about 1/4 turn on it each time. You can still get it with a spanner but if you have a low frustration tolerance....

[defever]

Update!

So I had a chance to load the car (one passenger, two bikes and some camping stuff) and drove 200+miles on the weekend to test my turbo…

I can feel the turbo kick in at around 2000rpm and it stays strong as far as I was happy to push. It went to limp mode only couple of times. By far, the way I had to drive to really push the turbo was nowhere near and definitely not how I drive normally. Although I did experience limp mode, I am happy to conclude that the turbo is in working order well within my driving needs.

I think the hose replacement did help a little; spraying the MAF sensor with cleaner probably did help a little, too; and probably the biggest help was working the actuator with a screwdriver. That must have released some carbon and now the vanes are moving more freely.

This made me wonder: When is limp mode not a problem? Will limp mode kick in with any turbo (new or used) while driving at high rev for long enough? Surely that’s not nice on any engine and turbo to stay on high rev for long period of time and I’m sure that’s not how car should be ridden (unless if you’re boy-ricer or racing on track/rally). Will a cleaned / refurbished turbo ever go into limp mode?

I suspect that the turbo will become sluggish again once the carbon builds up again. Also I need to look into the oil deposit on the outlet tube on the intake side of the turbo. So the turbo will have to come out sometime soon but the urgency has decreased a little. The vacuum pump arrived while I was away so I might exercise the actuator to free up a bit of carbon deposit from time to time.

I’m very happy that I’ve done the troubleshooting with the help of everyone on here (and potentially saved loads of money). Thank you so much to everyone. My friend with VW T4 van said that her engine is not as powerful as before (limp mode alert!) and I looked into the engine bay and her OEM braided hoses were shredded to bits. I worked the actuator rod and it was moving fine so I told her about my story (which I’m sure it went right through her head). I felt like a mechanic and I was proud!

Thanks everyone once again. Another amateur mechanic being educated by the wisdom of this forum!

[Doctle Odd]

The turbo should kick in at 1000 RPM

[defever]

I think I have demonstrated my ignorance.

I figure that turbo is in fact constantly on and it is load dependant rather than rpm... I felt the boost, or sudden surge in power, at around 2000rpm but I now understand that this surge will come on at different times depending on the load, road, gear and everything else!

Everday is a school day... thank you Dotcle for correcting me again.

[Doctle Odd]

I'm not trying to patronise you mate. The VNT turbo is designed to boost from very low revs that way there's no turbo lag compared to other types of turbos. It's usually the vanes sticking that lowers boost. I know stripping the turbo is a little daunting but it's like meeting the wife's father, never as bad as you imagine and 2nd time et al it's easier still.

[defever]

Good morning!

Yes, I didn't feel that you were being patronising. I used the hand vacuum pump yesterday evening to check the actuator movement and oh my, the movement is very sticky. At 15mmHg the rod sticks half way and it needs a good help from my finger to go all the way to the end.

So I have to get the turbo out in the end and clean it with Mr Muscle. It looks like I will be taking the intake manifold ant the cat as well! I might do a "how to" on these if I can manage to take some photographs!

[Cavanmick]

No need to take the inlet manifold off lad, take the air filter box and pipework out of your way and you can get the turbo out on its own

[defever]

Thanks Cavanmick,

I was referring to the other thread about EGR delete and Doctole suggested taking the manifold to clean the soot and Zollaf is now saying get rid of cat as well while I'm at it. Yes, I can see that the turbo can come out from the top (just neet to get under the car to undo some bolts on the exhaust side and oil down pipe, I presume?).

One potentially stupid question: the rubber tube that comes out at the mottom of the air intake on the turbo (where I have the oil residue); is that air or coolant pipe? The pipe goes deep into the bottom of the car and looks like it's going to the direction of the bonnet / radiator...

[Cavanmick]

It's the intercooler pipe buddy, no coolant pipes on the turbo.

[defever]

Okay, thank you Cavanmick. I thought so, but it looked like it's going to the radiator (I guess to cool the air) and I didn't want to spill collant all over the place.

Oh this is getting exciting!

[Cavanmick]

Will be no problem to ya.

[Doctle Odd]

Ask Zollaf about an oil he uses to clean turbos, I'm betting it's better than Mr Muscle. Hopefully you aren't using a Haynes manual as they tell you to put the lock carrier in the service position to remove the turbo. keep us updated :)

[green A8]

Zollaf is now saying get rid of cat as well while I'm at it.

Err.I'm not too sure you can rip the cat out of your exhaust now. I think that that rule was changed when the DPF deletes were outlawed. I've not checked with VOSA on this but I'm pretty sure i read or was given this info somewhere

[green A8]

I rang up our local MOT stations. All three confirmed that a cat must be present if one was fitted when the car was new. Someone mentioned a date 1991/2 I think but being an idiot I didn't write it down. This is a requirement for for the MOT regardless of the fuel type used, petrol or diesel. I suppose you could 'gut' your cat, but as I've never tried to do this on any of our cars I can't really comment further.

[Doctle Odd]

I rang up our local MOT stations. All three confirmed that a cat must be present if one was fitted when the car was new. Someone mentioned a date 1991/2 I think but being an idiot I didn't write it down. This is a requirement for for the MOT regardless of the fuel type used, petrol or diesel. I suppose you could 'gut' your cat, but as I've never tried to do this on any of our cars I can't really comment further.

It's not really a cat Mr G it's a soot box, there's no lambda before or after I think it should be ok to fit a straight pipe.

[green A8]

I did try to press that point D.O. But, all three MOT examiners were in 'Them's the rules' mode. I had a look on that hated place the online auction site. There are quite a few sellers flogging de-cat pipes that really do look like a pukka catalitic converter is still fitted. I have to wonder what if any difference to the emissions test the cat makes.

[defever]

UPDATE on the turbo!

So I had a go on removing the turbo on Friday (doing EGR removal did help to clear some space)... It took nearly 6hrs! Most of the time was spent trying to access some tricky bolts, especially the turbo support bracket underneath and the oil return bolts. Others were fairly easy once I removed the air box, N75 and vacuum reservoir to create more space. The exhaust bolt between EGR and actuator was indeed difficult to get to, I could only get "1 click" turn on the ratchet so that took real patience.

This is what it looked like inside the turbo…! (165,000miles):

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I couldn't believe the amount of carbon deposit... some were crystallised and really stuck on to the ring and the vanes...! There's no way Mr Muscle could have removed any of that in situ.

First, I used the wire brush bit for power drill to scrub off the big bits of carbon by hand:

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A lot of it just brushed off easily (and made a lot of mess so make sure you do this outside or have a massive rug to cover the floor). Then I rinsed it lightly with brake cleaner and toothbrush (it washes the carbon really well). I then used Mr Muscle to get into the exhaust intake and into the vanes. I tried to unscrew the three tiny bolts that secures the vanes but I nearly stripped one of them so I aborted dismantling further. 20min of Mr Muscle soaking, then rinsed with brake cleaner and this is the end result:

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The vanes now moves freely by hand, the actuator goes all the way up by hand, and I can hear the turbo instantly when I press the pedal! I did about 200miles over the weekend and there's no limp mode, there's no sudden surge of power at 2000rpm, and no fault code!

[defever]

Couple of notes to take:

Oil was leaking from the return pipe (has been seen by a garage earlier this year and they replaced the gasket, but still leaking); I put a new gasket but it's still leaking. I'm not sure if I screwed the nuts tight enough as it was very hard to get to the nuts, but I now realised that I could have taken the return pipe from the engine end. I need to revisit this.

Also, when I took the turbo out, there was a little oil residue on the intake turbine; I'm presuming this is expected and is fine unless there's oil pooling in the intake? The intake pipe didn't seem to be grotty with oil.

In terms of how to clean the turbo once removed, I think a combination of manual brushing with wire brush, rinsing with brake cleaner, soaking Mr Muscle as per instruction on the can and rinsing off with the brake cleaner again was a good result. Injecting Mr Muscle in situ on a high mileage car will not remove all the carbon. Maybe enough to remove carbon to notice a immediate difference, but it will soon soot up again. I wonder how Innotec works but the principle would be the same, I think. They have three bottles: 1) the foamer, 2) rinser, 3) fuel formula to prevent further deposit build up.

So, besides the ongoing oil leak issue, I think the task is complete! I wouldn't have done this without your help from here so thank you thank you thank you for all your advice and suggestions. lots of time spent but £££ saved!

[Doctle Odd]

Well done and I bet you had a smug grin when you finished!

[defever]

Yes I did, a smug grin on my sooted up face and clothes. Thank you Doctle for your help.

I need to get the return pipe sorted for oil leak. I should have sorted it out when the turbo was out but I didn't know the pipe could have been removed at the engine end. I think I need to unscrew the banjo bolt from the engine end, remove the pipe, clean it again and re-fit it.

Would a silicone grease help for better seal, or is silicone bad on places near oil?