How noticeable is a misfire on a V6?

[nsa]

My friend has an immaculate 2006 Mercedes S350 petrol V6 but it suffers from vibration throughout the rev range, in and out of gear. It doesn't stall and makes good power. No CEL light but it doesn't feel or sound right, more like a 1990s diesel. I read balancer shafts can be an expensive problem on these but they are usually accompanied by CEL, which this one doesn't have. Youtube research suggests changing the spark plugs and cleaning the MAF, which I will help him do this weekend. I have a cheap OBD reader somewhere and see if there are any codes. His garage suggests engine mounts. I'm concerned this is just a guess and an excuse to fit some new parts. There is no noticeable shunt in the driveline, just constant vibration in the engine.

I know what a misfire on a four-pot is like, but how noticeable is one on a typical V6?

Incidentally, the car is apparently worth about 4000 pounds (if fixed). It is immaculate, 67,000km, all the toys work, including the air suspension. I couldn't believe how much value there is in such a relatively new car. I don't have the space but if I did...etc etc...

Edited by nsa on Wednesday 3rd April 12:22

[Steve_D]

If you have an infra red temperature gun you can point to each exhaust manifold and look for a cylinder running at a lower temperature.

Steve

[Sardonicus]

Check the gearbox mount/cradle these have a habit of failing prematurely causing the gearbox to have metal to metal contact on the cross member only ever experienced this on diesel models but it feels bloody awful in the cabin , worth checking

[anonymous-user]

significant misfire should result in a Flashing MIL and a code being set by the OBD system


You can check by pulling off one of the injector plugs and rev ing it

[stevieturbo]

gas analyser will easily show a misfire.

Or even lambda trims would give an indication, assuming all other aspects of lambda feedback are working correctly.

But how noticeable any misfire will be...depends how bad it is and who is noticing it lol.

[Saleen836]

I had a misfire on my V8 (broken coil pack) and it was very noticeable

[Sardonicus]

Max_Torque said:

significant misfire should result in a Flashing MIL and a code being set by the OBD system


You can check by pulling off one of the injector plugs and rev ing it

This ^

[nsa]

Thanks for the tips. Fingers crossed it's a bad spark plug, coil, or the MAF. Any kind of mount trouble will complicate things.

[E-bmw]

As you have been told above, any one of those would almost certainly result in a CEL/fault code.

If there are none start by looking at engine/box mounts/gearbox issues.