v70 2.5T engine judders when accelerating

[VOLVOBOY]

Hi.
Just a few questions....
Is your car auto or manual ?
Does your car show symptoms when cold , when warm or both ?
Does it have a fuel pressure sensor on the fuel rail ?
Any mods on engine ?
Has it shown symptoms since having work done ?

[V70Zig]

Diesel man myself, but having read quite a few threads on here............
What make of spark plugs are in there....just a guess.
Your answer my well provoke some educated replies or may not.

[jimjam54]

It's an Auto engine. Seems worse the hotter the engine is. I can do a whole motorway journey with very gentle acceleration and won't notice it but as soon as I put engine under greater load or acceleration it will start to judder. If I drive hard it will get bad very quickly, but only when warm, and far worse when hot. Garage has replaced plugs and coil-packs. No difference on either occasion. Only codes ever shown was misfire on 2 x cylinders; that was when rpm actually decayed to zero after very heavy juddering/power-loss. Car was ok but fragile after 10 mins leaving engine off. That's when garage replaced coil packs to the 2 cylinders that had the codes, but no difference; although car hasn't actually broken down again to be fair...
No mods on engine and don't know if has fuel pressure sensor on fuel rail I'm afraid, but many thanks for the post...I'm stuck...

[VOLVOBOY]

Hi.
If it`s not a misfire due to electrics then it must be fuel/air related.
What was the condition of the old plugs - weak on fuel - I wonder ?
On warm-up the engine management is demanding extra fuel . That may make a misfire less noticeable .When hot the fuel trim is lower , possibly to the point of being almost weak. So when you make a heavy demand ( flooring the throttle / lugging the engine) there`s a misfire.
It doesn`t sound like a vacuum leak as high vacuum is at idle / light load and you say the car seems OK then.
It could be an induction pipework leak which would cause weak running .The engine management will try to compensate as much as possible.
If there is a fuel pressure sensor on the end of the fuel rail it could be faulty.
They are a known problem on earlier petrol P2`s.
Also there is a fuel pressure regulator mounted with the fuel-pump. These can fail. Later P2`s have a fuel pressure control module . This can be affected by water ingress and corrosion.
I would check this area first. If it`s not ignition and it`s not fuel and it`s not air leaks then move on to other areas such as turbo, engine earth-leads or the engine management.
Keep us posted.

[jimjam54]

Thanks so much for the comprehensive advice Volvoboy. I'm no mechanic so I'm gonna take your advice to my local garage and see what they can possibly do. You've been most helpful - i'll let you know how things turn out...