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Old 20th November 2017, 16:28   #1
EHD1978
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Default 2.5 KV6 Slight Hesitation

Hi everyone,

Can anyone advise please? My KV6 75 Contemporary SE, has developed a new problem over the last week. When accelerating, the car hesitates a bit but then still continues to drive normally. At a constant speed, the car is fine, and when accelerating hard, but it's mostly felt when accelerating at lower speeds. It feels like slight fuel starvation, and is felt as a slight judder in the car, to the point where a passenger can notice the hesitation. Does anyone know where I should start investigations?

The car starts normally, and has not cut out or died thus far.

Many thanks.
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Old 20th November 2017, 16:43   #2
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By the sound of things it looks like your ViS motors are not doing their job.
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Old 20th November 2017, 16:51   #3
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I had a similar issue a few years ago in my 1.8T - it turned out to be a failing ignition coil.
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Old 20th November 2017, 17:10   #4
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Originally Posted by Jim Jamieson View Post
By the sound of things it looks like your ViS motors are not doing their job.
When the VIS motors weren’t working on my old V6, it just lacked power. I didn’t encounter any hesitation as such from this problem. I did have a slight destination but that was down to a blocked CAT.
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Old 20th November 2017, 19:35   #5
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Start with the basics before anything else. Your car needs air, petrol and spark. Check air filter is clean, all petrol hoses are in good nick and spark plugs / leads are in good condition (when were they last changed?).

I would be looking for a split in a rubber hose somewhere between tank and engine allowing air to be sucked in. Also worth replacing the fuel filter if it hasn't been done in a while. These are things which should be done as normal maintenance anyway so worth checking.
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Old 21st November 2017, 08:20   #6
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Lack of power when the engine is under load along with a juddering does sound like a coil pack on the way out. Try accelerating from a reasonably low speed in a high gear up a hill. If that makes it misbehave then that's certainly worth looking at. For confirmation warm her up and disconnect your ht leads one at a time. The one that doesn't make much of a difference is probably the culprit.
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Old 21st November 2017, 16:29   #7
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Quote:
Originally Posted by Lord of Hog View Post
Lack of power when the engine is under load along with a juddering does sound like a coil pack on the way out. Try accelerating from a reasonably low speed in a high gear up a hill. If that makes it misbehave then that's certainly worth looking at. For confirmation warm her up and disconnect your ht leads one at a time. The one that doesn't make much of a difference is probably the culprit.
This too. If it is your coil however, it's often bad plugs and / or leads which cause a voltage overload and NAUGHTY WORD-NAUGHTY WORD-NAUGHTY WORD-NAUGHTY WORD-NAUGHTY WORD-NAUGHTY WORD- it up. So consider all 3 in your investigations rather than one or t'other.....
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Old 21st November 2017, 16:30   #8
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Quote:
Originally Posted by BillyRover View Post
This too. If it is your coil however, it's often bad plugs and leads which cause a voltage overload and NAUGHTY WORD-NAUGHTY WORD-NAUGHTY WORD-NAUGHTY WORD-NAUGHTY WORD-NAUGHTY WORD- it up. So consider all 3 in your investigations rather than one or t'other.....
I did not know that was a naughty word lol
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Old 21st November 2017, 17:27   #9
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Also worth replacing the fuel filter if it hasn't been done in a while.
Billy; I agree with your general advice on checking basic items but it is not a good idea to disturb the fuel filter on the petrol engines. This could easily induce the famous 'separation' problem leading to a breakdown. It's best to let sleeping fuel filters lie.

Simon
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Old 21st November 2017, 18:41   #10
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Quote:
Originally Posted by SD1too View Post
Billy; I agree with your general advice on checking basic items but it is not a good idea to disturb the fuel filter on the petrol engines. This could easily induce the famous 'separation' problem leading to a breakdown. It's best to let sleeping fuel filters lie.

Simon
There's usually a clip you can buy to prevent separation of fuel filters - not sure of the setup on these tho so I'll bow to your superior knowledge ...
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