Odd engine faltering when cruising?

[PeteJG]

Having just had the swirl flaps replaced, my '10 reg automatic R-Design ran fine for about a week although there was still a little vibration when I put it in reverse.

Suddenly though, yesterday, we started getting something similar to a faltering seemingly from the engine, just a little now and again, with an apparent slight loss of power. It's similar to what you might get with a dodgy spark plug or lead, but obviously it's not that. It seemed to occur mainly (but not 100% exclusively) when running at a constant speed in 6th gear, i.e. not when accelerating or slowing, and apparently not when the box was changing gear.

Now today it's got worse and more frequent, and the engine service notification has popped up although this could be just coincidence?

I'm guessing there could be one or a multitude of reasons, and no I haven't got a vida box so I can't look for any codes. There are various threads on here talking about "judder" but none seem to sound enough like what I'm seeing to be applicable. I'd like to think it's something easy like the lower engine mount, but could it be just that? It's been tipping down outside all day so I've not been under it to look.

[gmonag]

It could be a seized brake caliper.
Check for hot wheels.

[PeteJG]

Yes I did read that hat had been the problem for someone so I did go put some knuckles on discs .. and found nothing noticeable. Can that really cause the faltering though, particularly the intermittent nature of it? I've had binding calipers before on Audis, Peugeots and even my old VW Fastback many years ago, but they've never caused the enigne to falter like that?

[Tannaton]

Try turning the traction control (DSTC) off (button on earlier cars, in the menu on later models).

This is the only system on the car than can override commanded throttle level, if you have a cracked ABS ring or damaged sensor/wiring it can cause the issue you describe.

As always, get it plugged in to VIDA for any fault history - the "Engine Service" message is there for a reason.

[PeteJG]

Hmm ok, took it out for a test run just now - good idea about switching the DSTC off but sadly that didn't do it. It's still an intermittent "cogging" feeling, of varying severity and often (but not always) with slight power loss.

Front n/s brakes do seem to be running a bit hotter than the others, almost (but not quite) too hot to touch and I have noticed a very slight pull to the right when braking so I guess I'll be looking at that whatever happens.

Is it worth investing in a vida box? If so, has anyone got any recommendations for something which is economical but worth having?

[SwissXC90]

Originally Posted by PeteJG

Is it worth investing in a vida box?

Absolutely, if you plan to maintain and fix the vehicle yourself.

It's a complete diagnostic system, parts catalogue, technical description, fault-finding and parts replacement documentation system.

[PeteJG]

It turned out that the "cogging" effect was bad contacts on one of the injector plugs, cured by pulling the contacts out of the plug shell and squeezing them up a little for better connections. As expected though, if one needed attention it probably wouldn't be long till the others needed doing too, and hey presto another one's started doing it now so I guess I'll be doing the lot at some point. Looks like I also need the vacuum mounts doing too ...

So does anyone have any thoughts or knowledge on why the Volvo engine is such a source of vibration that it needs specialised mounts in the first place?

[Harley Dave]

"Luxury"

Cheers

Dave

[TruckbusUK]

Originally Posted by PeteJG

So does anyone have any thoughts or knowledge on why the Volvo engine is such a source of vibration that it needs specialised mounts in the first place?

Probably due to the inherent instability/vibration of 5 cylinder engines (144° power strokes,)
Audi/VW have similar specialised mounts for their 5 cylinder engines, probably so do Honda/Acura, Fiat/Alfa Romeo, Ford/Mazda, Mercedes-Benz & Land Rover (well maybe LR are too agricultural for sophistication ) and any manufacturer that uses or has used 5 cylinder powerplants.

Just my guess and certainly not a Volvo "only" issue.

[Harley Dave]

I wondered about 5 cylinder engines (and engine mounts) so went and did a search...

This is from "Car and Driver" (2012)

Five-cylinders do not suffer from the shaking forces that keep four-cylinder noise-and-vibration engineers employed.

Their main faults are primary and secondary rocking couples that cause the engine to oscillate in the vertical plane.

An engineer on one early Ford project noted: "When that engine was running at high speed, it was going back and forth every which way.

You got scared to look at it."

But simple counterweights attached to each end of the crankshaft correct the primary couple; the secondary-imbalance flaw is generally minimized by careful tuning of the engine and transmission mounts.

Truckbus - you have nailed it.

Cheers

Dave