The power loss happened in two places once when the car had reached almost the highest point that I wanted to travel at -about 80mph but also when moving at at 50mph. sorry no fault codes yet - but I will ask the garage.
The car just appeared to hold its speed but if you depressed the accellerator pedal it would not respond so I suppose it trips out
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Many thanks for your referral to the similar problem - this are exactly the same synptoms - I'm back in to the garage on Tuesday.
I presume the vw fault finder software starts by advising to replace certain components first starting with the cheapest before raising the stakes with more costlier items.
Any other ideas Timaru? I am grateful for your advice. Thanks
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The new intercooler seems to have done the business, they left the invoice for the part in the car £220 and spent all day fitting it @ circa £45 per hour - thank God they were paying!
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Credit where credits due, it's Screwloose that's the expert here, if you look knowledgeable and quote his suggestions to the fitters they look at you in awe and give you the mechanics version of the Masonic hand shake when you leave!
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On a similar subject, my Passat Tdi 110 (AFN) suffers a loss of power where the turbo would normally be noticed. No fault codes and it's not overboosting. Taken turbo off and stripped. Surprisingly clean and vanes move smoothly. However, the actuator, under vacuum does not move the vane actuating lever up to the stop. Total movement on the actuator arm is 7mm but will go further if assisted by hand. I suspect I need a new actuator. Can anyone please advise?
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Somebody posted this link, which shows the VNT15 turbo gizzards: www.technologie-entwicklung.de/Gasturbines/VNT15-T...l
Might help - cleaning seemed to sort it out in the given example.
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ianden
Before going down that route, I'd think about scanner testing/replacing the MAF sensor. [Genuine part straight from the dealers ONLY!!!] No power and no codes is the contaminated MAF sensor's trademark; an under-boost fault will usually set a code and maybe cause black smoke. If the boost-control system manages to achieve it's programmed pressure using just the available actuator travel, then that's clearly all it needs.
Fortunately, one of the few well-sorted bits on a VW is the self-diagnosis system; in most cases, the codes actually mean what they say. There's a few French manufacturers that could take note!
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thanks Screwloose,
What I forgot to mention is that although no fault codes came up, only 2000mbar of boost maximum was indicated when it should be 2300mbar (this diagnosis by VW diagnostics instructor with the appropriate laptop etc.) and we both thought it would be due to gummed up variable vane mechanism. It isn't, the mechanism moves smoothly but the actuator does not move the vanes through all the available movement yet I cannot find a leak on it, it holds vacuum.ianden
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Thought I'd better add: there's no noticeable smoke from the turbo, no obvious play in the turbine, it spins freely and the fault isn't intermittent. There is definitely insufficient boost from the turbo. ps that german site (entwicklung.de) is informative and is what prompted me to suspect dirty turbo mechanism and strip it down (which is fairly simple). Howevre, in this case wrong diagnosis.
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ianden
What year is this one? AFN's went on for quite a while and there are two distinct manifold pressure sensing systems on them. The early ones use a hose from the manifold to the MAP sensor mounted inside the ECU. That hose has issues. Never trust the accuracy of the live-data pressure reading on one of those - test with a direct-fed gauge.
The later combined MAP/inlet temp sensors are desperately unreliable too. You wouldn't believe how many times one of those has been found to be the root cause of 17964/5 - usually just after a grands-worth of VNT has been fitted! VW keep 300 of them in stock at their central parts!
Have you checked every single hose-clip on the pressure pipework? Rust-failed clips are common - always the ones that are near-impossible to see. Usually sets 17964 though.
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Screwloose,
It's a late 98 UK spec import and definitely has a combined temp/press. sensor in the charge pipe. I've also checked pressure with a direct reading gauge which, whilst not as sensitive because of the capillary tube I used, showed a similar maximum pressure (1.1 bar above atmosphere). First thing I did was check all pipework, then intercooler which I cleaned and can confirm is clear. I've checked resistance of the vacuum control valves, they're OK but I don't have values for the temp/pressure sensor which I also suspected. However the diagnostic guy reckons that's OK cos he took the pressure readings off it. I'm willing to test it though if I knew how.Please explain what you mean by 17964/5, is that a fault code?
Cheers,
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ianden
Looks like you really have got low boost. Double check those hose-clips; it can be really hard to spot the rusty one. Don't forget the exhaust side of things, [cat?] or the air filter. On the MAP/IAT sensor; pin 1 is the right-hand one looking into the sensor's plug. 1 is earth; 2 is the temp - 5.00v regulated feed - current measured; 3 is another 5.00v feed.
Measure the MAP's output between [connected] pin 4 and earth. It's given spec is a roughly linear progression between 0.5 volts at 35kPa and 4.5 volts at 250kPa. [That doesn't make the slightest sense; but then - when did kPa ever make sense! Add some noughts or bring back lbf/sq" and inches of Hg.]
The IAT is simply measured resistance between [disconnected] sensor pins 1 and 2. 2-3,000 ohms @ 20C: 2-300 ohms @ 90C.
Code 17964 is achieved boost level lower than ECU demanded: 17965 is over-boost.
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Screwloose,
With a decent vacuum the actuator works OK so I've put everything back and, as expected, things are the same.
Air filter is new although when I first had the power loss I checked it and it was absolutely filthy (only 15k miles) and misalgned but changing it didn't help. As far as I know the exhaust is OK but if the cat is causing an obstruction how would I know, fuel economy is fine.
I'll check out the sensor as you suggested but I'll also replace all the vacuum hoses and check the efficiency of the vacuum pump. I don't suppose anyone knows what vacuum it is supposed to pull by any chance?
Thanks for your input so far, really excellent.
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This can occour when the cat falls appart inside, if that's the case, switching the engine off for a few seconds can instantly resolve the problem. Maybe worth checking.
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Fortunately, one of the few well-sorted bits on a VW is the self-diagnosis system; in most cases, the codes actually mean what they say. There's a few French manufacturers that could take note!
My experience in this respect is quite different! I have many instances where the VW system reports lamda fault, so VW change the lamda probe, only to find (at the customers expense) that the fault is not rectified... The lambda senses the problem caused by another faulty component which doesn't initiate its own fault code.
Also, the mk3 MPI Golfs are well known for having regular intermittent engine stalling/cutting out which doesn't initiate any form of fault code.
Other manufacturers may be worse in this respect, but the vw system is FAR from flawless.
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mark25
That is a slightly different point to the one that I was making. The dealer's alleged "knee-jerk" reaction to any particular fault code is a staff-training failure - not the fault of the self-diagnosis system. Codes are often, wrongly, considered replacement instructions - they're not - they're meant as guidance to the trained and experienced.
If the system shows a oxygen sensor code for - say - "low sweep rate," then that isn't carte-blanche to start throwing parts at it. It merely means that the whole fuelling system may have strayed outside it's set parameters - at some point - and it merely gives a starting-point for a considered diagnosis. The code will nearly always be for an incorrect SIGNAL from the component; it doesn't necessarily follow that the component is itself faulty.
If the stalling issue you mention occurs within the bounds of normal operations, then no code will - or should - be logged. The various Mk III Golf systems are far less sophisticated that the latest ones; but even they won't detect a stall, because it's within the expected range of possible driving conditions. If every time someone stalled the engine it put the MIL light on, then I'd be snowed under just clearing ECU's.
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Screwloose:
It may well be a different issue, but for a system to work, all the parts of the overall process need to be covered. ie fault -> ecu -> code -> reader -> user -> interpretation -> solution -> check solution -> etc
Now in the case of the latest generation ecu's from VW this goes wrong at the very first step! WHY? because in a lot of cases the ecu is constantly dealing with errors from the low quality (relative to earlier generation efi ecu's) sensors, so much so that a real fault can be just a statistically greater than normal error occourance. In principle the modern ecu deals with this by having lots of software code to ignore the 'normal' errors (including a system which works out the fueling in reverse, 2s compliment, to capture the errors the ecu is throwing in itself for good measure). The problem is that the actual cause of a a fault is very often not monitored by the ecu or not the first sensor to go out of 'normal' limits.
There are similar issues with other steps in the process, but i see no value in going into that in such detail here, it's not constuctive.
Now you seem to have got your head round the system and are able to interpret some of the codes to good faultfinding effect. That's good for you. That's also good for the members of this forum because you willingly share the info/knowledge on here, excellent! very comendable! But it doesn't patch the holes in the whole process, especially those which seem to be costing the man on the street with a mk4 generation golf and a turbo obscene amounts of money un-necessarily. This is why i'm not so inclined to support your praise for the system...
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I did spend half an hour writing a long and considered response to that. It got chopped in half and then lost when I tried to post it. Ah, well...
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Ctrl C and V are your friends on this forum...
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Sorry for being away so long but I've been trying to fix this wretched car. After Screwloose suggested the Cat I removed it and checked it. It did seem partially blocked so I replaced it (£104 from GSF) and... no difference. At the same time I stripped the turbo again and nothing seems amiss. The actuator IS working OK and fully moving the turbo vane mechanism. The vacuum produced at the actuator is fully moving the actuator. I've by-passed the control valve and still there's no power. I've changed the fuel filter, and air filter, and now the cat, had a diagnostic, no faults indicated and the turbo has no apparent fault yet there is no power. What I haven't yet tested is the MAF or MAP sensors as suggested by Screwloose but after those I'm at a total loss at what to do next other than take it to a dianostic specialist to charge me lots of money for saying there are no fault codes, which I already know.
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ianden
A good diagnostics guy should be able to see a lot more than the codes. It's the live-data from the ECU that will show a fouled MAF or a unstable MAP sensor reading. Is your boost pressure OK now that the actuator is moving correctly?
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Have you tried driving with MAF disconnected?
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Screwloose,
The boost pressure is not OK and that's with a direct reading pressure gauge. The actuator probably was working OK before it's just the test equipment I'm using now is better. Of course if there's insufficient exhaust due to fuelling problems that would limit the turbine speed.
The diagnostics guy should be a good one as he is an instructor in the system; he found no faults and he did spend an hour on it. He reckons it's a jamming turbo but out of all possibilities I now think that a turbo fault is least likely, it certainly is not jamming. Following Ashok Leyland's suggestion I disconnected the MAF and there was a definite increase in power, nowhere near the right amount but absolutely definitely a significant increase. Disconnecting the MAP caused no turbo function at all, the vacuum dropped to zero. I'm not sure what this tells me about the health of the MAF (i don't have test figures e.g. resistance etc.) but I bet someone knows what it means. I'm on the brink of buying a new MAF (£53+ vat from GSF for a Bosch unit) so it anyone thinks I shouldn't then please tell me tonight!
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Ian - the new intercooler sorted our "almost" identical problem, have you had this looked at?
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Timaru, yes, looked at that early on. Took it off, cleaned it, no sign of a leak, and put it back. Also checked all hoses etc.
Thanks anyway.
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I have the same symptoms, the dealer (for £44) diagnosed MAF and left it disconencted which improved driveability, but as you say still far from normal. I have had the problem for 3 weeks now, I took it to the dealer a week ago, and have been waiting for them to get a new MAF since then. They said there is a worldwide shortage!
If you want to wait, hopefully I will get one within a few days and repost the outcome here. They will charge me £136 fitted, I know I can get one for £85 from them and fit it, but if they have misdiagnosed, I'll not be easy to get a refund, so I told them to go ahead. GSF and ECP don't have my part number :(
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Unfortunately I'm going to Cornwall next week fully loaded and I'm really keen to sort it before then so I don't struggle on the hills. However, it is improved with the MAF disconnected so I may wait for your progress report. What car do you have?
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There's a reference here www.tdiclub.com/TDIFAQ/TDiFAQ-7.html#l to checking the MAF with VAG-COM, which might help diagnosis.
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Hello, I have an 02 Passat with AKN tdi engine.
I have been informed by the VW dealer today that when they ordered the part it was showing a 1-2 week backorder and now shows 'no longer available' The lady had a lengthy discussion with VW yesterday about this and they have sourced an 'alternative' part which was about 3x more expensive, and she managed to get goodwill from VW to make it only 50% more expensive.
It is true - you never buy another Volkswagen!
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Screwloose, Ashok Leyland,
Eureka! The problem is now fixed. I bought a new identical Bosch MAF from GSF for £68 incl., fitted it there and then (5 mins. how much does VW charge?) and lo and behold not only has the lost power returned but it now accelerates strongly all the way from 1500rpm to 4500rpm whereas, ever since I've had the car, some 30 months, it's had a power band from 1700rpm to 2900rpm then flat.Whether it's all down to the new MAF or the new cat and cleaner turbo have contributed I can't be sure but it's great now. Just think, I almost paid out for a new turbo based on the diagnostic. Sometimes you must just heed your own judgement aided by experiences from others such as yourselves.
Thanks for your contributions, this is a great forum.
Hope your Passat goes as well as mine when your MAF is replaced Ashok Leyland.
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ianden
Really glad to hear you're fixed: it's way back now, but do you recall my initial answer to your original post......
No power and no codes is the contaminated MAF sensor's trademark.
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Yes I do and I owe you a drink or 10. It took me a while to be convinced but backed up by disconnecting it as suggested by Ashkok Leyland finally pushed me in the right direction. I don't regret the taking off of the turbo and strip down nor the changing of the cat cos it was all good experience and I know exactly what state they're in now.
Cheers.
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Well, I had my new MAF fitted today, I set off from the dealer and the car was no different at all. I stopped and opened the bonnet, a brand new MAF and housing sparkled before me. I turned around and went back, and they had another look and said the computer says the MAF is faulty again, they are having it back for all of Wednesday, hopefully 4th time lucky!?
The dealer was pleasant enough and negotiated an excellent goodwill price with VW so I don't mind paying for the new one just to have a new one with a 2 year warranty, hopefully, it won't be so expensive to cure. I don't think it's the wiring as it's better when disconnected, but maybe there are several pins and only one has no signal?
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Some MAF's get a different power supply after the engine's been switched off. There's a high current flow through the sensing element to heat it to a high temperture for a few seconds. This cleans the element by burning contaminants off. It could be worth going through this stage before writing a new MAF off. New ones could well get grease or dust on them.
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Hey all, first things first, I'm not sure how to put a new comment as I'm a newbie!!, but I have a similar problem, sometimes my car cuts out under high load, 50-8mph, turn ignition off and back on and it's fine, if it happens enough then I get a light on which I've diagnosed and it comes back as "Overboost", the car apparently had a 180map
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