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Hello, I'm a bit stumped here and hope someone with more experience than me can help.

I recently had a 100K service and the timing belt changed on my 2001 2.5tdi T4. During the belt change the chap said he altered things a little as the marks on the pulleys didn't quite line up. The effect being the engine should run better.
Immediately after the belt was changed I noticed the engine fires up on the first turn (it wasn't bad before by any stretch but is definitely better). Now, however, I find there is a LOT less power all the way up to about 2000-2100rpm (but particularly between say 1700-2000) up until the turbo kicks in. The power curve was very smooth before right through the rev range and now it gets progressively more gutless until the turbo starts, which it does with an almost violent increase in power. The problem is such that pulling onto a busy roundabout is now very difficult/dangerous as the van is slow sluggish in the early rev range.
I took it back for the guy to have a look at, and although he didn't run any diagnostics he said what a number of other forum posts point to - that the air mass sensor (a bosch one) had given up. I don't want to waste the guys time by asking him to look at the engine again unless im sure and I really cant afford to have a diagnostic check done or by a new mass sensor on the off chance! Also, I find it hard to believe that the sensor happened to -out during the service.. a bit too much of a coincidence?! I disconnected the air mass sensor (as advised) to try driving with it disconnected and it feels a little better but the turbo has almost no effect.
Has anyone had a similar experience following a timing belt change?

Thanks in advance!
 

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Hello, I'm a bit stumped here and hope someone with more experience than me can help.

I recently had a 100K service and the timing belt changed on my 2001 2.5tdi T4. During the belt change the chap said he altered things a little as the marks on the pulleys didn't quite line up. The effect being the engine should run better.
Immediately after the belt was changed I noticed the engine fires up on the first turn (it wasn't bad before by any stretch but is definitely better). Now, however, I find there is a LOT less power all the way up to about 2000-2100rpm (but particularly between say 1700-2000) up until the turbo kicks in. The power curve was very smooth before right through the rev range and now it gets progressively more gutless until the turbo starts, which it does with an almost violent increase in power. The problem is such that pulling onto a busy roundabout is now very difficult/dangerous as the van is slow sluggish in the early rev range.
I took it back for the guy to have a look at, and although he didn't run any diagnostics he said what a number of other forum posts point to - that the air mass sensor (a bosch one) had given up. I don't want to waste the guys time by asking him to look at the engine again unless im sure and I really cant afford to have a diagnostic check done or by a new mass sensor on the off chance! Also, I find it hard to believe that the sensor happened to -out during the service.. a bit too much of a coincidence?! I disconnected the air mass sensor (as advised) to try driving with it disconnected and it feels a little better but the turbo has almost no effect.
Has anyone had a similar experience following a timing belt change?

Thanks in advance!
Get it on VAG diagnostics equipment to check/set your timing. Sensors could be checked at the same time. It sounds like your fuel pump timing's too far advanced.

edit: These engines need proper equipment and a bit of practice to set the pump timing correctly. It is set mechanically and checked using diagnostics equipment.
 

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hi mate, going through exactly the same problem after my cambelt was changed, had the diagnostis done and it throws up the diesel pump timing as the issue and it cannot be cleared, had it checked and its way out and needs adjusting, apparently whoever changed it used tipex as a marking point to put the timing back right:confused:

Im just in the process of getting mine done...good luckT:
 

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Hi Guys,

I have T4 2.5 with 195000km on the clock and yesterday for the first time I experienced a similar power loss. The first 5km everything was OK and then suddenly a significant power loss (I could hold the speed but it would hardly accelerate). I stopped the car turned on the engine and everything went back to normal. But this morning on the way to work it happened again.
My first thought was the mass sensor, but you mentioned somthing about a fuel pump timing or failure.

Fact is that since several month I'm wondering if there is a problem with My fuel pump because if my fuel tank is below 1/3 I often have a hard time starting the engine and it seams to get worse.

So now I'm wondering if these to issues could be related !?

Anybody ??? :*
 

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If the thermovalve on the return pipe back to the fuel tank is faulty, then it will draw air into the fuel lines, as the return pipe sits higher in the tank than the pick up pipe which will still be submerged. Don't buy a pattern one, a genuine VAG part is about £14. It's the plastic part clipped into the top of your fuel filter
 

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Thx Skippyroouk ! I ordered this part today and will mount it tomorrow. I'll let you know how it goes T:

Do you think this could also love the problem of the power loss ? Or should I look elsewhere ?

The guy from VW told me it could be some kind of turbo security gate that could start to disfunction randomly shutting the turbo down in safty mode. Could that be ?
 

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I've got a 2.4 AAB, so no fancy electronics or turbo for me! I'd guess you have another issue, sounds like the turbo is cutting out, which from what I understand it is likely to be a component giving a fault when it has got some heat into it, hence the cut out when warmed up fully. You could do with getting it plugged into vagcom to give you a better prognosis.
 

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Cuckoo have you solved your problem ? On my side I cleaned my turbo and injection system by running it 20min on Liqui Moly Diesel Jet + I cleaned the air mass sensor by dipping it in break cleaner. Since I done 5000km and the problem never reappeared ! Moreover the turbo "sings" much more, I have less smoke and over all I have the feeling I never had so much power since I bought my T4 2 years ago T: This liqui Moly stuff was not cheep and hard to find in my area but I'm stoked by the result. (I have no LM shares I:)

About the return pipe issue, I have replaced it like you suggested Skippyroouk. The engine starts a little better but now when I have less than 20liters in the tank the engine can suddenly shut down as if I ran out of fuel. It happened to me three times now after 4km suddenly no engine + almost no more steering and no more breaks :eek: And it take some time before I manage to restart the engine.

I double checked that the return pipe is mounted the right way around (with the arrow to the tank) and just can't understand what I could have done wrong !? Could the return pipe be defective ? By curiosity before mounting it I blew thought both entries and noticed no anti return !? If anyone has a clue...?
 

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It only works when wet, I did the same as you, then tried it in water and it worked! Sounds like you may have an issue with the pick up in the tank. When did you last change your fuel filter?
 

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Hello, I'm a bit stumped here and hope someone with more experience than me can help.

I recently had a 100K service and the timing belt changed on my 2001 2.5tdi T4. During the belt change the chap said he altered things a little as the marks on the pulleys didn't quite line up. The effect being the engine should run better.
Immediately after the belt was changed I noticed the engine fires up on the first turn (it wasn't bad before by any stretch but is definitely better). Now, however, I find there is a LOT less power all the way up to about 2000-2100rpm (but particularly between say 1700-2000) up until the turbo kicks in. The power curve was very smooth before right through the rev range and now it gets progressively more gutless until the turbo starts, which it does with an almost violent increase in power. The problem is such that pulling onto a busy roundabout is now very difficult/dangerous as the van is slow sluggish in the early rev range.
I took it back for the guy to have a look at, and although he didn't run any diagnostics he said what a number of other forum posts point to - that the air mass sensor (a bosch one) had given up. I don't want to waste the guys time by asking him to look at the engine again unless im sure and I really cant afford to have a diagnostic check done or by a new mass sensor on the off chance! Also, I find it hard to believe that the sensor happened to -out during the service.. a bit too much of a coincidence?! I disconnected the air mass sensor (as advised) to try driving with it disconnected and it feels a little better but the turbo has almost no effect.
Has anyone had a similar experience following a timing belt change?

Thanks in advance!
If you want to bring this to me I will get some live logs and diagnose correctly,

Regards

Dan 07974522666 or 01803522666
 
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