Hello,


I recently purchased a 1998 Volvo S90 with a 24 Valve In-Line 6 Engine. When you start it sometimes it hesitates to start and once it does start it's a rough idle. The check engine light stays on solid and blinks anytime I do even the slightest acceleration. The code turns back a Cylinder 6 Misfire, so I replaced all 6 plugs and then replaced the cylinder 6 Coil as well. The problem still persisted after all of this work and I plan to take it down to the shop tomorrow to get it looked at and fixed. I purchased this vehicle with 75000 miles so any helpful hints would be greatly appreciated.

Wiring to the coil might be bad.
You might have a burnt valve.

I had the exact same problem on my 1997 S90. Check engine light was on and the engine would ide rough and sounded like it was going to stall. Theengine light would flash intermittently briefly at low speeds and rpm's.However the car would drive fineover1500rpm.Shortly before this problem I noticed that while driving at around 80-100km/h the car would surge or chugwhenI would accelerate. I took thecar to the shop andOBD said engine misfire cylinder 1 and 3.It was determined that the spark plugs (original Volvo ones, in terrible condition) weres the culprit. The problem still presistedand after2 days in the shopchecking fuel pump, injectors, ecm, modules, etcI took it to another mechanic who told me itwas the intake manifold gasket and injector rings.$87 in parts and$100 in labour. The car drives fine now.He said this useually happensin thewinter becauseof the hotfrom the engine and cold air causes these seals to break, especially if you dont warm up the car before driving it fast... ie highway, etc.This could be your problem...
hope this information helps and good luck