V70 2.5T AWD 2004 Only rough idle; all else is super.

BrianIwasiwkaC30V70 · Post by **BrianIwasiwkaC30V70** » 07 Apr 2025, 08:18

Replaced spark plugs, coils, cleaned throttle body, replaced crusty vacuum hoses, clamped others, replaced timing belt (water pump), replaced cracked intake "pipe" from filter to turbo and thermostat housing due to leaking second layer gasket, replaced fuel filter and intake air filter. Injectors have been professionally cleaned with new o-rings. Otherwise, everything works fine on the car; no hesitation, super acceleration, very smooth on the road/highway. But at idle, it sounds and feels like a truck. It idles at around 680, steady with no variation. I've run a few Motul engine flushes over the past year or so and I think it sounds better every oil change and the more it is driven. But, if there is something else I am overlooking please share. 236,000km
Thanks,
Brian I (new)

Post by **scot850** » 07 Apr 2025, 08:26

Is the car throwing any codes at all? Normally when they are not happy they will throw a code to give you a clue.

Neil

Vova585 · Post by **Vova585** » 07 Apr 2025, 08:55

It sounds like your car is doing quite well. If it is able to idle steady at 680rpms it is a very good result. Rough idle, IMHO, is unsteady rpms on idle, misfiring on 1 or more cylinders..
If you have access to good scanner I would check if it has any volvo specific codes and also what fuel trims it is running while idling.

Havoice · Post by **Havoice** » 08 Apr 2025, 00:45

The steady idle at 680 RPM suggests that the ECU isn’t compensating for misfires or leaks, so it’s probably something affecting the vibration or fuel-air mix rather than a major mechanical fault.

Vova585 · Post by **Vova585** » 08 Apr 2025, 07:24

Expending on Havoive suggestion - have you checked the engine mounts?