Sharan VR6 Mis-firing, Shuddering & Poor Acceleration

[Carouser]

Hello All

I have just noticed two other recent posts on the same subject but referring to the 2.0 petrol engine and 1.9Tdi. Thought I'd post a thread on the VR6 engine for some help then contact the others to share the love, as it were...

Basically, my 1998 Sharan VR6, 108k miles has started to develop a mis-firing problem.

It started last week, and would generally be intermittent. It was mainly felt when the car was at a stand still and idling, when the car would notably rock from side to side and the engine felt like it was running on five or fewer cylinders.

The car would pull away okay, but I would experience some hesitation in first and second and I'd notice a significant reduction in power and acceleration in all gears, although eventually it would make it to 75mph crusing speed.

The engine also sounded notably different (like a V5 as opposed to a V6)

After say ten minutes of cruising at speed, the problem would seem to rectify itself and all would be fine again, until maybe a day later when it would do it again.

The car was due for a service anyway, so I booked it on Friday. I picked it up a day later, and after paying a whopping £1,080 for a full service, (plus two new tyres, brake discs and pads all round, two sections of exhaust and two anti-roll bar links) the car is running worse than ever and it's getting increasingly so.

I took it out for an 80 mile run yesterday evening; the first 2 miles were perfect; The next 30 dodgy; The the next 40, awful and the final 8 just plain painful.

It is struggling to accelerate in any gear with notable stuttering and shuddering particularly if I am heavy with the accelerator. Again, it will get upto a desired crusing speed but takes a whle, but any heavy pressure on the accelerator results in lots of shaking and hesitation especially when under load. Cranking the engine over 3,000 rpm or more helps to reduce the symptoms but then I end up doing stupid speeds in places I shouldn't.

At idle, there is a notable mis-firing, random 'throbbing' for want of a better word from the exhaust.

Bascially I can't drive it as it is and wouldn't want to risk going any further than the 1 mile back to the garage.

My initial thoughts were an ignition problem such as faulty spark plug, or maybe the HT leads aren't making a good contact, but then I had assumed that the full service would have sorted this. Indeed, the garage had said that the previous owner (or their chosen garage) had been lazy in servicing the car as the front three spark plugs had been changed regularly, but the back three hadn't been changed at all for many years which is a common thing as they are difficult to get at apparently. Still, having been assured that all six had been replaced it hasn't improved matters.

15 years ago I had an XR3i and experienced a simliar problem and it turned out to be that the carbon core in the distributor cap had basically cracked and splintered and only a tiny piece was making contact with rotor arm. I'm not sure what the equivalent of this might be on the VR6.

Or, I wondered whether one of the lambda sensors might be at fault, in light of the exhaust sections being replaced, although this wouldn't count for why the car was experiencing mild symptoms BEFORE the garage had carried out work to the car.

The only other possible things I can think of are maybe a fuel delivery problem, or timing problem.

Has any one else experienced this problem at all with their Sharan, what ever engine you might have?

The car goes back to the garage this week, so when (if) it is repaired, I'll post a follow up with their findings.

Many thanks all

[Carouser]

Right, problem resolved.

Apparently it was the HT leads arcing. I thought these would have been replaced as part of the full service, especially given the spark plugs were changed, but apparently not.

The old leads were dreadful, and hadn't been making proper contact with the back three spark plugs, hence the arc.

A new set (and another £100 later) and we are back in business.

Thankfully...