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Old March 2nd, 2008, 10:11   #1
TDIFanatic1.9
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Default Guru's pls help. Stuck on holiday limp mode while towing caravan

Hi There

I Scanned with vag-com and got a positive boost deviation intermitend error. Unfortunately didn't copy the error.
The limp mode only started yesterday while towing my caravan on some uphill roads. It also didn't start emediately only after a few km's of hard road. Reset by cycling ignition. On flat road only happens after a long drag and car worked hard otherwise flat road seems fine. I cannot simulate it with out the caravan and some long uphill drags. It seems to have something to do with something getting hot and sticking, when I stopped for food it cooled down and didn't happen again imediately, only again after a few km's of hard road. I checked the actuator function, it seems fine (cold engine, cannot test next to road laptop batery flty).

Please I'm towing home after 10 days and its uphill most of the way, I need the turbo to work.!!!
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Old March 2nd, 2008, 12:27   #2
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If the actuator is free and there's no leaky vacuum hoses, maybe try flushing the n75 valve out with some brake cleaner?
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Old March 2nd, 2008, 14:55   #3
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fault finding list.

faulty vacuum lines, sticky VNT actuator, failing N75, partially clogged intake manifold, large boost pipe not secured properly with a small leak at full boost.
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Old March 2nd, 2008, 20:18   #4
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I'll work thru the list by replacing the vac line's. The actuator I tested with vag-com and seems to move freely-dont know if it move's its whole range thou. The intake I took a peak at and its not clogged. I'm sure I'll hear a boost leak if there was any.?
Question: How do I test the N75 for functionality? Can I swap it with the egr valve, is the egr valve's response time the same as the n75?
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Old March 3rd, 2008, 06:38   #5
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You can swap it. It'll work temporarily.
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Old March 3rd, 2008, 06:55   #6
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Check that the vacuum line going to the actuator is not loose and falling against the block. It could be collapsing when the engine temp is high. Check my signature for the usual stuff.
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Old March 6th, 2008, 21:44   #7
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I'm having trouble finding the correct spec and size pipe. The shops only carry fuel and oil line and only stock 3.2mm and 5mm. The pipe looks pretty firm so will probably work for vac purposes, but what to do on the 4mm hoses, can I use the 3.2 and ream out the ends to fit over the 4mm nipples?
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Old March 6th, 2008, 22:11   #8
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sounds like the obvious is being overlooked stoptowing .....thats your problem get a dodge with a cummings and all will be well ....set that aside ..pull the intake boot and clean the egr valve and load up with vacum what may be happening is your boost is loosing through the egr and goes into limp mode the reason this happens under heavy load is that your ecm is used to no load its not a stored dtcso a key cycle will clear probs but its all in your dirty egr/ cooler call me crazy but it s common
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Old March 6th, 2008, 22:24   #9
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Quote:
Originally Posted by TDIFanatic1.9
I'm having trouble finding the correct spec and size pipe. The shops only carry fuel and oil line and only stock 3.2mm and 5mm. The pipe looks pretty firm so will probably work for vac purposes, but what to do on the 4mm hoses, can I use the 3.2 and ream out the ends to fit over the 4mm nipples?
Correct size for the larger vacuum lines is 5mm. Many of us use 4mm silicone for them because we can't find 5m silicone.
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Old March 12th, 2008, 07:33   #10
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Quote:
Originally Posted by dr.diesle
sounds like the obvious is being overlooked stoptowing .....thats your problem get a dodge with a cummings and all will be well
Most of us can't afford 2 cars or a dedacated towing vehicle so the jetta will have to do for the od time's I get a break and go on leave. Most tows are not that far. The TDI engine produces enough torque to be a great towing engine with very good fuel returns.
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Old March 14th, 2008, 00:07   #11
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Ok So I got home at last but I had the limp mode again even after changing the vac hoses. I then changed the n75 around with the egr valve and blocked of the egr vac hose going to the egr intake pipe as dr. diesle sugested that a stuck open egr valve might cause a los in boost through the egr. Well that sertainly made a diference as I was able to tow a lot harder and longer before the limp mode returned. It also only went limp once after about 250km of towing where it would previously go out every 20km.
This is the error recorded by the ecu.

1 Fault Found:
17965 - Charge Pressure Control: Positive Deviation
P1557 - 35-10 - - - Intermittent

What does this fault mean, is it over boost, under boost or what.
Fault only ocurs when towing and only after long uphill's in 4th, Problem cannot be replicated without the caravan in tow.
I tested the n75 and vnt with vag and all seemed fine, is it posible that the vnt can get sticky only when the turbo is very hot after serious uphill towwing.(long full boost run)?
Since the problem improved after I swopped the n75 and blocked the egr vac line, could the egr still be leaking at high engine temps.?
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Last edited by TDIFanatic1.9; March 14th, 2008 at 00:43.
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Old March 14th, 2008, 05:58   #12
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How much weight are you towing?

Just another thought to consider...
Since this seems to happen at the exremes of power, It sounds like you are working the little motor too much, full power up hill at sustained max boost, and may just need to back off the throttle a little.

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Old March 14th, 2008, 08:11   #13
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Put in a boost gage and drop into 3rd gear on the steep hills.

IMHO if you are towing you also need an EGT gauge as you are pushing maximum fuel and boost on a hill pulling a trailer.
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Old March 14th, 2008, 08:43   #14
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[quote=TDIFanatic1.9]Most of us can't afford 2 cars or a dedacated towing vehicle so the jetta will have to do for the od time's I get a break and go on leave. Most tows are not that far. The TDI engine produces enough torque to be a great towing engine with very good fuel returns
I understand ,Idont have a big truck the point is your car is not designed to pull a trailer the engine has the torque but the tranny cant handle it, have you ever put a new maf on your car?
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Old March 14th, 2008, 14:02   #15
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Whaddya mean "your car is not designed to pull a trailer"? That'll be why the manufacturer offers towing brackets that attach to pre-designed, certified mounting points then...
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