T4 transporter limp mode issue.

Thank RJ,came up as security alert ,the reply was drafted several days before and added to till ready to send ,so most likely my bad ?.
Moving on as I have been doing a ton of research ...I call it goldmining as it like sorting the gold flakes from the stones lol unless going to specific forums, common issue with these vans is limp mode and the most common problematic parts are the control system for the turbo whether its a 1.9 or the 2.5 5 cylinder motor ,sometimes it is as simple as vacuum leaks but mainly a bad N75 or N18 solenoid ,ether valve will throw a code if not working or out of operating range.
My plan is to test mechanical function of associated parts before diving in and buying part ,end goal will be to get it running better to get it scanned with VCDS ,have done the following in the last few days ;
Tested wastegate operation ,applied 10psi to actuator and operation is normal showing even 5 psi is enough to get opening movement ,also tested it under vacuum of 15 psi and it held so I know the internal diaphram is ok ,
remove vacuum hose banjo fitting on turbo inlet and found it partially blocked clear out and clean ,
revist plastic turbo inlet pipe ,found it to be out of round and not a great fit on sealing "o"ring ,made a former to go inside it and heat it then fit band clamp around it ,let it cool and check it as round again ,test fit with new "o" ring ,now as it should be,
test N75 and find it leaking between vacuum and discharge ports ,tested just overlimit with ohms test ,have a new one to fit,
recleaned EGR inlet pipe as was previously 30% blocked with carbon ,egr valve retested but same result and non functional ,will consider removing or blanking ports on the solenoid controller ,ether way it will tidy things up ,
fitted replacement PCV sealing grommet .
Will report on progress when I do further electrical tests cheers.

 

After research it indicates these valves are the same and do the same function , vacuum @ to top port ,pressure out to wastegate next port down ,lower port is used back to turbo inlet pipe nipple ,both the n75 and n18 share the same function and are used differently to achieve the same result ,IMO its a generic term for this valve , as confirmed by senior member on VWT4 forum and they can be swapped as he had done on his van,others tried it to same effect.
Cheers

 

The banjo on turbo has pressure, when turbo kicks in.
95% sure egr operates on negative pressure while turbo works with positive pressure.
Get a rolling log done, with map, maf. Then you can see what the pressure is, what is requested, same for air flow meter.

 

My current plan is to close off EGR system as its non-functioning anyway but retain operation of N239 solenoid which to my thinking is protection incase of a "run away " ,have tested the function of the valve actuator and it holds vacuum well , I hope to test soleniod when I get my battery sorted as well as other 2 pin plugs.
Replacement N75 fitted ,appears the old one was original.
Will report when more is done and I get close to a start-up,cheers.

 

Which T4 forum did you ask on?
My acv also does the same thing on occasions. Never got to the solution as yet.

 

Hi as mentioned above VWT4 forum in the UK,early days I was on another van forum (won't mention the name) ,posted asking some questions and got strange/smartass answers !!! ,for a moment I thought I was on a US forum lol ,but this was a UK forum .
Guys on the T4forum are helpful and polite and have been a great help ,would pay you to join up .
My main issues were caused by bad vacuum hoses to start with then went to permanent "limp mode" due several other causes which I have hopefully mostly sorted.
Cheers

 

All related components tested ,voltage to N75 is 12.4 volts ,all parts back on and nothing else to suspect,thought I would attempt to start but after checking oil level I found it to be above the top mark by a fair margin ,thought about it and remembered I had always checked to level after a run when hot,this appears this is not correct as mentioned in my Haynes manual as these engines require time to drain back from overhead gear to sump , can only believe this was the true level after the last oil service , so now I believe the cat convertor is blocked .
Unbolted it off the downpipe the following day and swung it to one side then started the van ,let it warm up then revved it and got boost ,cut the outlet pipe ,removed cat and found it completely blocked @ the inlet ,this now explains my previous backfires .
Plan was to build a cat delete pipe but this is illegal in my country so I will import new cat and pipe from the UK as only solution ,cheers

 

What country are you in?
There are available imitation cat exhausts that appear just like the real thing. Nobody would be able to tell.

 

New Zealand ,went to my local garage and he kindly bought up the regulations on his computer he mentioned our government upgraded the regulations recently and also commented it would need to be OEM style replacement with some proof of what it is ,its just not that simple if it was I would take "the easy road",cheers.

 

No problem. I feel your pain. It's a nightmare here too, can't change anything without permission.

 

Found a complete OEM style cat with pipe to first silencer ,183GBP and euro 2 spec , usual story shipping is worth more than the item but never mind ,hope to order next week after talking to my vehicle inspector,cheers.

 

Great, at least it's a solution.
My Golf has been with the mechanic for a while week and they still haven't fixed the hunting/idle issue.
The blue sensor should arrive Monday so with good luck........

 

Cat and pipe to first silencer arrived from the UK in 9 days which IMO is bloody good service,however with Ebay Global shipping it should be fast as it costs SO much.
A very nicely made part and fit was great ,nice to be not crawling under the van anymore....getting too old for that now besides ,rechecked the oil level before starting it when down of the jack and the 900mls I drained put it below the top fill mark so safe on that .
Got it out from the back garden and waterblastered years of green slime off it ,test drove it the following day and no further issues ,I would say it is going as well as it was before my issue but thats not correct.....its in fact going a LOT better so can only presume the cat was partially blocked when I bought it .
Very happy with the result ,currently sorted central locking and need to get A/C tested , the rest to do is mostly cosmetic as van is very tidy ,cheers.

 

Excellent news.
Nice looking short nosed. Very clean.
What's you plans for him?

 

Sadly it will be up for sale ,was going to be converted to camper but plans have changed ,hoping it will sell quickly as it a rare spec in my country and is in great condition ... not your usual knocked around commercial ,cheers.