Hi All, I live in South Africa and drive a 1999 2.5 20 valve S70 normally aspirated motor. It has developed a misfire between 2500 and 4000rpm. Below that and above that she is smooth as silk. The engine warning light flashes as the misfire starts. I am running out of optiond short of going to the local Volvo Stealership. Any ideas? All suggestions welcome! Regards, Dick

 

It is usually either bad spark plugs or bad coils.

 

I replaced the plugs with OEM and checked all the wiring to the coils for abrasions, cuts etc but found nothing. I have always thought that either coils work 100% or not at all? Perhaps I am in need of some education here!!! Is there an easy way to check the coils without the OBDii software and a scanner? Thanks for the input.

 

The coils usually break down when you accelerate. About the only thing you can do is check the coils them selves for cracks. The coils are very common to go bad. I usually reccomend if one is bad to replace all to save the hassle from doing it again in a week or month later.
If you could get a scope hooked up to it then you might be able to see the misfire.

 

Thanks for the input. I think I will just replace the lot.