Jerky S80 - help

I have a '99 S80 T6 with approx 140,000 miles. This morning the "Check
Engine" light went on and the message window started displaying the
"Emission System Service Required" message (it's not the gas cap). Here are
the current symptoms:

Very rough idle
At very low speed 5-10mph major jerking
Ride becomes smoother with higher speeds
At 50-80 mph the "Check Engine" light flashes about once per second instead
of steady on, and the ride is fairly smooth.

Any ideas/clues would be appreciated! Thanks, in advance.

Alex L.

 

My guesses without getting an OBDII code would be either a misfire (bad
coil pack or plug for one of the cylinders) or a faulty O2 sensor. I
believe either would send the emissions related message. As engine RPMs
climb the two problems mentioned would seem to lessen.


Jordan 1999 S70 Loaded!

 

Jabber:

Great diags!!! Was a misfire due to bad ignition coil. Thanks!