rondocap

So about 20k miles ago, I changed the spark plugs on my S55. I did not change the wires, they are original 137k miles right now.

Recently, I have noticed a bit of an interrupted idle, it's not a smooth surge like before, but a bit rough; and after coming to a stop after highway driving, it's more pronounced.

I am not sure if there is a loss of power across the band, but I suspect it's a little bit different..the roughness is just at idle pretty much, not when in higher rpms.

I ruled out a mass airflow sensor, as I was told the symptoms differ and I'd get a check engine light which I don't have, so are the spark plug wires the culprit here most likely?

rondocap

Also, I checked with an obdII scanner and did not get any codes or malfunctions, everything is fine...will a bad wire not throw codes but still cause a rough idle?

Arnee

Bad or broken wires should throw misfire codes.

rondocap

I have an Autel ODBII Scanner, and I didn't see anything codes - do you think if I take it to a mercedes specialist and they run a more in depth diagnostic they can find something? I already took it once, and they just listened to it and suggested wires, but did not can the car.