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Discussion Starter #1
Hi guys, I've been having problems with my 2002 1.9 Tdi (PD, engine code ARL).

I've replaced the turbo (old one had leaking seals & left a fair bit of oil in pipes & intercooler) & just had a new camshaft & timing belt fitted (as old ones had turned to chocolate!) & head removed & skimmed.

I've got an EGR delete & have removed ALL the vacuum piping from the anti-shudder & EGR valve.

I've also replaced the vacuum tubing from the N75 to the turbo & to the accumulator & vacuum source- (that's the only vacuum tubing I have now)

I also swapped around the N75 valve & the one next to it.

The garage confirmed that it holds a vacuum OK & the turbo actuator moves fine - also checked with VCDS.

I've replaced the MAF too.

I've been having the 17964 code & limp mode whilst under load - if I thrash the car through the gears then it seems OK, if I put it into 4th early & just hold my foot to the floor, it goes into limp mode every time.

I'm now thinking about doing a boost leak check (when I replaced the turbo, I visually checked all the pipes etc & all seemed OK!) although I'm not getting any black smoke out when I accelerate (as I've been told I would with a boost leak).

On a diesel, should I block off after the EGR delete (where it goes into the intake) & pressurise from just after the MAF or should I let the pressurised air into the block & see what happens?

Assuming it shows no leak, my next plan of attack will be :

* MAP / temp sensor (no code shown though)
* Possibly a blocked CAT?
* Tandem pump (putting out enough diesel pressure?)
* Check / replace the injector loom
* Is new turbo screwed already - does the VNT actuator need major adjustment??

Earlier yesterday, I fitted a new MAF (as old one was 4 years old anyway) & went for a drive & logged the info...

- 1st run was in 3rd from around 1500rpm & it didn't drop into limp mode.
2nd run in 4th gear did go into limp mode....
This problem has only happened since I replaced the turbo - before that, it hadn't ever dropped into limp mode, so I guess it's something I've done but I have no idea what it can be!


The only vacuum tubing I've got is from the vacuum source to the N75, from the N75 to the turbo & N75 to the air box. There are no other lines (I've blocked off the one to the accumulator (ball) as the ball is leaking slightly).


I've done the output test on the n75 & it seems OK - I could see the actuator moving with no problems (it is a new turbo after all).

This is the engine data with it turned off:


and with it at idle :



This is the 1st run, 3rd gear from around 1500rpm & it didn't drop into limp mode:



and this is the raw data from this run :



This is the 2nd run, from 1500rpm in 4th gear which DID drop into limp mode (again) :



and this is the raw data :


MAP - I haven't touched & it looks like it hasn't been off the pipe that goes from intercooler to EGR delete in years - screws all rusted up...
Airfilter I actually removed for the 2 runs as it got wet
Turbo actuator not loose either.

Have just been out & taken off the hoses (& the pancake tubing) either side of the intercooler & checked again for leaks & replaced a couple of the green seals too.
All seemed fine (yet to do a boost leak check as I need to make the leak detector!)
FWIW, it was run for years with (by the look of it) a cheap ebay type tune up device which went between the feed to the injectors.
I took it off a few years ago when I had the turbo & camshaft replaced the 1st time (4yrs ago).
It started smoking (whiteish smoke) on startup & when booting it hence I replaced the turbo (quite a lot of oil in the intercooler pipework but I haven't been able to remove the intercooler itself to completely clean it but pipes are cleanish).
When I was doing the turbo, I checked the cam & followers & they looked like they were on the way out again so I had them replaced along with having the timing belt done.
The garage said one of the head bolts was loose (jesus) so they took the head off & had it skimmed as the head gasket looked slightly iffy.


Anyone got any ideas at all? (and sorry for length of post but hopefully there's enough info!0


Many thanks for any help with this poxy problem!!
 

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I'd definitely do a boost leak test. I think the idea is to check the intake hoses so just pressurize it up to the engine. If you pressurize the engine it's a leakdown test. I think the EGR block is causing the MAF readings to be so different but can that cause limp mode by itself? I can see how the MAF and boost suddenly drop off when you went into limp.

Are you chipped? Why does the MAF specified call for 850 when the engine is off? It looks like it never moves. It should be low when the engine is at low rpm and go up. I think those tuning boxes can play with the sensor readings, is it removed now?
 

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Discussion Starter #3
Hi Blackcat,
I was thinking much the same so I'll block off after the EGR delete & pressurise after the MAF...

I removed the cheapo tuning kit a while back so there is nothing there but as to whether it has been chipped before I got the car - I don't think so as the previous owner (5yrs ago) was a middle aged lady with dogs!

I've got a replacement MAP sensor which I'll fit in a bit & a brand new N75 valve (garage owed me one!) so along with the brand new MAF, I'm running out of things to replace!!

Am wondering if it may be something to do with the CAT.....:dunno

Cheers,
Nic
 

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Discussion Starter #4
Well, I've done a boost leak test (as best I can) & it doesn't sound like it's leaking.....
:-/
 

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Discussion Starter #5
Right, managed to mash a hole in the CAT so it will definitely flow better & I adjusted the stop screw on the turbo IAW VW spec (.002" feeler doesn't bind @ 17" but holds the feeler @ 18" - it was set too long).

Went for another drive & it seemed marginally better @ low RPM (turbo actuator stop), it still went into limp mode in 4th gear @ 2400rpm again :-(

Running out of things to check now!!!
 

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Someone else found that there was built up carbon stuck in some of the vacuum ports. Try cleaning them out. And triple check the vacuum routing and hoses.
 

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empty the oil out of the intercooler. check the short vacuum tube, controls boost at 2400rpm mine had a crack in it and caused the exact same problem at 2300 - 2400 rpm! mine had dried up the crack wasn't audiable or visually noticable until we got it off and bent it beyond normal.
 

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Discussion Starter #8
Cheers guys - there doesn't seem to be much oil left in the intercooler (and I'm getting next to no smoke from the exhaust).

I replaced all the vacuum tubing from / to the N75 and have checked that with a mityvac vacuum tester & all seems OK....

I also get good vacuum from the tandem pump / vacuum source too!

It does seem to be lacking power going up hills - although not as noticeable as before I put a hole through the CAT & adjusted the turbo actuator stop!

Only manage 33mpg on an hours motorway run (@ 70-80mph!) so something is still not right!
 

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Discussion Starter #9
Someone else found that there was built up carbon stuck in some of the vacuum ports. Try cleaning them out. And triple check the vacuum routing and hoses.
Not sure what you mean by vacuum ports? I've replaced the N75 for a brand new one & with EGR delete, it is the only vacuum device there now...

Thanks through!
 

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Have you checked the vacuum pump? IIRC somone had the big tube and the hose coming off it loosen up. It looks like the difference between specified boost and actual boost is quite a bit. My guess is that it's something related to boost control.
 

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Discussion Starter #11
Yup, the vacuum pump seems OK & was pulling 25-27"Hg.
Agree tho - something to do with boost control but what? I'm going to try & adjust the actuator arm & see what difference that makes....
 

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wow400,

Have you sorted the problem? I have a very similar problem.
I have the same fault code - 17964. Mine is due to my inability to generate more than 1675 millibar of boost!.

The ECU requests more boost - it does not get it and goes into limp mode.
I have tried almost everything:

Boost leak test - no fault found.
Borrowed a known good MAF - no fault found.
Checked/swapped the N75 valve - no fault found.
Vacuum leak test - no fault found.
VNT linkage is free (unbolted actuator) and moves when engine starts.
Cleaned EGR valve for good measure.
Temporarily sleeved the pipe from the airbox to the turbo - no difference.
I even took a massive risk and permanently applied a vacuum to the VNT actuator, at least this eliminates turbo control from the ECU. However I still only 10psi gauge pressure of boost.

The only thing I can do now is check for a blocked cat.
Could it be low fuel pressure?
Could the water trap need emptying?
Could the fuel filter be blocked?

Additional info:
There seems to be allot of oil coming from the compressor side of the turbo. I do need to take the bottom (metal) boost pipe off and see whether there it a massive amount of oil in the bottom pipe causing a obstruction. However I had this pipe off when I did the boost leak test, I didn't get a flood of oil. If the compressor seal has gone, I don't see how this is costing me the 6psi that I am looking for.
Even though the VNT linkage is free and moving, could sooting up of the VNT vanes still be an issue? The problem occurred suddenly, fine one morning, shagged in the afternoon, so I don't think it is VNT vanes.
Cycling the ignition clears the problem, but I go back into limp mode as soon as I request more boost approx 100 - 3 miles depending on how heavy my right foot is.

Does anyone have any other suggestions?
 

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Low fuel pressure, water trap, is very unlikely.
Blocked fuel filter is more likely.

The oil is not related to your boost problem but "alot of oil" is not good. A little oil is OK. If there's enough oil to cause a blockage, it's enough oil to cause a runaway and hydrolock.

If the VNT linkage is moving well, the ring inside could still be worn and not moving the vanes. See this writeup: http://www.myturbodiesel.com/1000q/a4/VNT-turbo-removal-vanes.htm

 

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It was a blocked cat.

Well it turned out to be a blocked cat. (Matrix had come loose and turned)

However, the compressor side of the turbo is leaking oil. I shall have to get a replacement and swap it out.

As a side issue, I have worked on plenty of cars. I couldn't actually take the cat off, I had to smash the ceramic out. The only way I could see of getting the cat off would be to drop the bottom wish bone off and possibly remove and engine mount. All made allot easier if you have a four post lift. (Which I don't)

I also replaced the oil turbo feed pipe while I was in there. Don't even get me started on that, if I thought the cat was bad this was like changing a part on a car design by Beelzebub himself.

One of the most retarded designs I have ever seen. I might go into business selling replacement braided hoses for this job.
 

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Discussion Starter #15
Blimey, I'ver just been sent an email saying that someone had replied - I had missed the 2 previous posts!
I took my CAT off (on the ARL it's pretty simple) and although it looked OK, I smashed a hole through the stuff in the middle - I now have a replacement pipe which doesn't have a CAT which I need to fit at some stage & then see how it goes.

I think my car still won't be right - I'll need to take it to a tuning-type place to get them to check the fuelling etc...

When I replaced my turbo (bitch of a job for me!), I bought a braided replacement oil feed pipe - life saver!

Good luck!
 
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