I just picked up an S40 and it surges under acceleration when it's got a little more than 20% throttle. I'm almost certain this is ignition related, but I haven't even gotten into pulling anything apart yet. I'm brand new to this car so I'm at your mercy...

It appears the car has coil on plugs? One on each cylinder I presume obviously. Strangely enough someone on the forum said something about there being 2 ignition coils total for the engine (not 4), is this correct?

I'll most likely just get brand new plugs and coil-on-plugs, and I'm hoping that it's not a wiring things with the wires running to the coil-on-plugs, because that's almost certain to be off the main wiring harness, which would be a nightmare.

Can anyone give me a little insight into the ignition system on these bad boys, and what all I may want to look at to solve this problem before I drop $200 on coils and plugs?

 

Took it to a mechanic friend, on the way I started to suspect it wasn't ignition because if I sit at a light with the brakes on, and step on the gas, it doesn't shudder. Turns out most likely it's something with the drivetrain, hopefully just a CV joint needs to be replaced (most likely).

 

What did you find out?

I'm new to the forum, but when my V40 experienced random surging, it was the fuel regulator.