A cornucopia of bag things AHU related

avcentraltias

Well-known member
Joined
Mar 14, 2020
Location
Midlands UK
TDI
1z Powered T4 Van
Good afternoon everyone.

Friday night i got home late from 400 mile round trip in my AHU powered T4 Eurovan only to wake up the next morning to see a oily mess under my headlight. The van had been low on power on the way home but on closer investigation I see that two 10" long cracks had appeared along the welds of my intercooler.

With intercooler replaced I went for a drive only to notice thick clouds of black smoke coming along behind me so after returning home, to find a huge pile of soot on the driveway approximately where my exhaust had been only a few minutes earlier, I read the codes and saw "Intake manifold pressure too low". I had a spare turbo lying around so I fitted that, along with its N18, cleared the codes and went for another drive.

Now I have a fair bit more power than I did this morning but nothing like as nice as it was before I set off on Friday, but the black smoke has only been replaced by grey smoke, and although it drives smoothly the revs feel like the engine is "hunting". Fault codes are completely clear at the moment.

Where shall I look next?
 

avcentraltias

Well-known member
Joined
Mar 14, 2020
Location
Midlands UK
TDI
1z Powered T4 Van
Just tried a new fuel filter in the hope that would improve matters, but no luck. Same grey smoke, same "hunting", same feeling like the handbrake is stuck on..........
 

powermandan

Active member
Joined
Apr 5, 2021
Location
Worcester UK
TDI
ABL, AHU, AFN
Sounds like you probably still have a boost leak.

N18 is the valve for the EGR. I presume you meant N75?.

N75's are not all created equal. Some are designed for boost and some for vacuum. Maybe you fitted a vacuum one erroneously.

You need to use VCDS to really diagnose it. Could be loads of things that would be immediately obvious when looking at the data
 

avcentraltias

Well-known member
Joined
Mar 14, 2020
Location
Midlands UK
TDI
1z Powered T4 Van
Thanks for pointing my mistake. Yes, it's the N75 valve I've swapped. The one in the metal casing, rather than the black plastic one. The one thats on it now is from an AFN engine. Maybe I should swap them back again and see what happens. I'll do that and have another look at the pipes. Maybe one of those is split.

I'm using a free version of VCDS (lite). No doubt there's a better one to have but I don't use it often enough to warrant a subscription.
 
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avcentraltias

Well-known member
Joined
Mar 14, 2020
Location
Midlands UK
TDI
1z Powered T4 Van
Just put the old N75 back on but no change. New N75 just been ordered if only to eliminate one questionable component.

Also, I've just noticed it sounds like im low on compression on one cylinder. If I get time I'll compression test it this afternoon.
 

avcentraltias

Well-known member
Joined
Mar 14, 2020
Location
Midlands UK
TDI
1z Powered T4 Van
Just CT'd it but i cant remove the third injector (master injector). I can wiggle it a only couple of mm in its hole but I cant get any more movement than that and certainly cant pull it out. The other three injectors came out with only gentle persuasion and the compression test shows 380psi on each of those cyclinders.

Why do I get the feeling that something is very wrong on the inside of cylinder number 3?
 

powermandan

Active member
Joined
Apr 5, 2021
Location
Worcester UK
TDI
ABL, AHU, AFN
Just CT'd it but i cant remove the third injector (master injector). I can wiggle it a only couple of mm in its hole but I cant get any more movement than that and certainly cant pull it out. The other three injectors came out with only gentle persuasion and the compression test shows 380psi on each of those cyclinders.

Why do I get the feeling that something is very wrong on the inside of cylinder number 3?
Have you removed the injectors in recent history. First time I removed a set I had to buy the biggest slide hammer you ever seen to pull it out.

After that it's been easy. But if they have never been out they can be hard to remove
 

avcentraltias

Well-known member
Joined
Mar 14, 2020
Location
Midlands UK
TDI
1z Powered T4 Van
Actually Im coming to the conclusion that its the injectors that are at the root of all this. Looking at the three that have come out, the nozzles are almost completely "glazed". Absolutely no way atomised fuel can get into the cylinder.

The master injector is still stuck in there though. I have got it to turn freely in the hole, I can turn it with my fingers now, but I cant pull it out of the head at all.....

Does anyone know what size thread is on the end of these injectors? If i could find a nut to fit it I could weld it to a slide hammer like Powermandan suggests and persuade it out that way. The alternative is to remove the head. Gulp!
 

Mongler98

Top Post Dawg
Joined
Mar 23, 2011
Location
COLORADO (SE of Denver)
TDI
98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
The only way is woth a slide hammer. You will damage things if you do it any other way.
Yep. You can rent or make one for a few bucks.
It's a standard metric thread... not sure exactly what one it is.
 

avcentraltias

Well-known member
Joined
Mar 14, 2020
Location
Midlands UK
TDI
1z Powered T4 Van
Well that gives me more confidence to go at it with the slide hammer.

I'll drop some spare injectors into my diesel man later anyway. Chances are he will have something that fits.

Could someone confirm that's its the Bosch. 216 nozzles that I want him to install for a little more "zing".
 

adamss24

Veteran Member
Joined
Nov 2, 2005
Location
Great Britain
TDI
audi a4 2.5 tdi 98 quatrro 6speed
If you’re stuck for an injector puller then go to your local scrappy and find a injector pipe that fits on your injector(take a spare out and try) and weld it to a slide hammer. I have an inexpensive sliding hammer that costs about a tenner on Amazon, it’s meant for Bosch/Lucas tdi injectors… it’s short too and only weighs about a kg…
 
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