I have a 1993 850 GLT sedan that periodically hesitates or hiccups. This usually happens at about 35 mph. During the "hiccup" the check engine light briefly flashes.

Can anyone enlighten me as to what could be causing this?

Thanks.

 

Maybe a missfire due to bad spark plugs or wires.

 

If you've checked the plug and wires, and gone through things like the distributer cap and rotor, you may find the problem lies with the ignition coil, which has been my issue recently, get some ignition spray and spray it all over the coil to see if it improves.. Ive found you need quite a bit though.

 

Pull the code(s). That'll provide a better idea to determine the problem.

This will guide you:
http://www.troublecodes.net/Volvo/