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Discussion Starter · #1 ·
Hi
My T4 has a bit of juddering at 4000rpm when accelerating hard in 3rd (manual gearbox) gear. Not noticeble in 1st or 2nd gear. If I drive through the problem the car seems to lost it power. New coil leads and plugs have been fitted.
The problem can be worse some days than others.
I would appreciate any help on the matter
Thanks
 

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Discussion Starter · #3 ·
Yes both coils and the fly leads for cylinders 1 & 2. Also i have checked the condition of plugs lately and all are in good condition and burning evenly.
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But because they look good doesn't mean they are good how old are they?

They only have a life of 30,000 miles.
 

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I have exactly the same problem on my 1998 V40 T4. I have been chasing this fault for 2 years now. I have replaced both coils and leads and it has actually cut out on me. I am starting to think that it is fuel starvation / pressure drop to the fuel rail.
I have noticed that it is worse if you are low on fuel and going uphill it has actually ground to a halt. After waiting 10 minutes it will start up again and be fine for another few months.
I removed my fuel pump from the tank and found that it was covered in black dirt - including the whole of the tank inside. As a quick fix I cleaned up the filter on the end of the pump and put it back - hey presto no missfires for a few months.
I now intend to clean the whole of the tank out properly.
 

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Discussion Starter · #7 ·
PAULW when I asked Volvo about the problem they suggested a new fuel pump was the cure or the coils, unfortunantly a pump cost a lot of money £300. So you could be on the right track. Anybody does your car have a return hose from the fuel inlet manifold? mine does not yet the fuel pump has a return hose and the pressure side hose goes directly to the vacuum valve on the manifold. I can see a return pipe coming out of the manifold but no hose is attached (it does not leak petrol). Is there a better source for info on the Turbo models than the Haynes manual which has very little on the turbos.
 

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There are other manuals (and CDs) available but I am not sure how good they are - just did a Google search & they're out there.

What petrol are you using? The T4 is designed for & runs best on 98 RON petrol. Even Super Unleaded is only 97 RON - maybe you need to try several tankfuls of Shell Optimax (98 RON) to clean your injectors etc. up & to adjust the ECU via the various sensors on the engine. Might need to run as many as 300 litres through the system to clean injectors/valves etc. thoroughly - the ECU will adjust timing etc. much more quickly than that.

Hope you find a cost-effective solution!
 

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Discussion Starter · #9 ·
I use the top quality fuels and have used fuel system cleaners which do seem to make a short term improvement.
Managed to get hold of a vacuum/pressure testing device and have found that the turbo wastegate valve will not hold a pressure. This would seem to be the fault with the car. I am guessing that a faulty wastegate will cause overboost of the air pressure and I believe the car has a built in safety feature that cuts the fuel ( same as the way the traction controll works ) in this overboost condition, can anyone confirm this?
Can someone tell me where I can get a new wastegate from? I suspect Volvo is quite expensive.
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I'm confused as to why the fault is only apparent in 3rd gear though.

Have you checked that your car has had any/all Volvo software updates?

Tech is your man for questions about turbos - if anyone can sort it out, he will.


On this forum, you're never.....
 

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Yes I beleive they have a cutoff for overboost.

Im not sure where to get one aftermarket.
 

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