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Discussion Starter · #1 ·
can anybody help me i have a 1998 Passat 1.9 TDi (110bhp)
the problem i have is when driving it hard after about 3rd gear it will lose power and go into limp home mode when i turn the ignition on and back off again it comes ok for a few mins then will do the same
i have tryed the usual things like replacing the MAF sensor ect i also changed the boost valve and tryed the other falves i could find
i also had a good look at the smaill pipes ect but cant see anything
i was told it could be possible turbo over boosting or loseing presure ?
p.s i am UK and its a 98 B5
 

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If this is a VNT Turbo model you need to make sure the VNT mechanism can move smoothly throughout the range. If it doesn't you will get poor performance, overboosting at certain rev's and probably a CEL eventually.
 

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I have a '99 TDI and in the UK also. Mine has around the 50K miles on it and is running fine, but just lately I have been experiencing flat spots from around 2 - 3K revs, is this how your problem started?

Sounds like some sort of regulator has gone, as the turbo could be overboosting and then under pressure. There are numerous diesel specialists in the UK, search on the net or hit the good old Yellow Pages, failing that if you can afford it, go see the dealer.

Cheers :thumbup:
 

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Discussion Starter · #6 ·
LIVE4SPD said:
If this is a VNT Turbo model you need to make sure the VNT mechanism can move smoothly throughout the range. If it doesn't you will get poor performance, overboosting at certain rev's and probably a CEL eventually.

How do i know if it is a VNT Turbo model ? and were is the VNT mechanism ?
 

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Its a VNT, Hammy.
It sounds like are both experiencing bad MAF symptoms even though Hammy replaced his once.
The TDI MAF's tend to be very costly; you can use a Mercedes Benz/Pierburg MAF ftom the 3.2 CDI or VW's own 2.0 (the 2.0 has an extra temp sensor - yet is substantially less).

Otherwise, check the VNT rod.

Another check might be to reset the frive by wire: turn the key to on (do not start), and depress throttle for 30 seconds. Release the throttle and start her up. Driveability should return.

It would be suspect if you had a clogged intake; your fuel is so much cleaner than ours.
 

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The VNT mechanism consists of a vacuum acuator and a rod that connects to a lever on the turbo. Not sure what engine you have but most of the newer TDI's had the VNT Garret Turbo, so I'm pretty sure you do too.

Find somebody to check your MAF first. It's easy to check and its' the cheaper part to replace.

If the vanes don't move freely with the VNT mechanism disconnected then it's new turbo time. ($$$)
 

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Do anyone get the a surge in engine revs on startup sometimes with a puff of black smoke. After that it appears to run fine but losses power at high revs? I went throught the motions (replaced the MAF, checked the VNT etc). Eventually it ended up being the fuel cut off valve where the "O" ring had come off the plunger. I replaced it and it has been fine since.

Oh and by the way... the dealer diagnosed it as a "possibly" faulty turbo and wanted to change it (£700). Fortunately for me, it wasn't and I have a habbit of not believing everything the dealer says.

:lol:
 
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