I have 260k on my 98 S70 and last night it started to misfire. I suppose it was a bit of luck as it only got bad after I had got back home. Was out for a short trip to the store and started to have a misfire here and there on the way back. Got it home with not much issue and parked it. Came out later tried to start it up and that is when the flashing CEL came on and very obvious misfire started.

About a month ago I replaced the plugs/wires cap & rotor with brand new OEM parts due to it stalling out on me once at an intersection.

This morning I went to the junkyard and got a Mass Air Flow sensor and Ignition Coil to see if changing those out made a difference. No help, but then again junkyard parts are just that. I pulled the plugs today to check the connections, I found a fair amount of build up/foul on them already.

I was also getting Gross Evap Leak code and Upstream O2 sensor weak signal code before all this started, I pulled the o2 and cleaned it. That was around four months ago.

If anyone has suggestions it would be greatly appreciated, thanks.

 

Sounds like the car is running rich. Maybe a vacuum line problem or something. When was the last time the PCV was replaced?

Did you clean off the plugs with a wire brush and double check the gap? Worse case is that you have a burnt valve, that would make it hard to start and run. Fuel pressure should be checked. Do you ever use fuel injector cleaner? Have you had a compression test recently?

 

There is two vac lines running out of the top of the air box, one with a rubber elbow and one with a plastic elbow. The plastic one is cracked and fell off, I still have it but it isn't hooked up. I have had never replaced the PCV, so that is at least 80k miles on it.

No to cleaning the plugs with a wire brush or compression test recently. I have used some injector cleaner before I replaced the plugs, just what ever brand was on the shelf of my local gas station though.

Thanks for your reply, at least I have some other ideas to try out now.