Hi, my 95 850 Turbo suddenly started to idle rough and shake when in drive and would eventually cut off. It works fine in reverse. For me to "drive" i have give it very little gas and then put it in neutral and glide. Any idea as to the cause? Thanks in advance

 

how old are your spark plug wires? same for cap, rotor, plugs? If you don't have a check engine light on yet it may just be a matter of time, then you can read the codes. Can you rev it when in neutral or park? did this come on suddenly after a fill up?

 

Relatively new spark plugs 2k miles max. The car is hard being used. Not sure about the age of the plug wires. Yes, it can rev in park and neutral. The car is used off and on like twice a month. I'm trying to make it my daily driver. She has not been used regularly since I upgraded to a BMW X3 three years ago

 

bad plug wires can appear as a misfire under load which can be mistaken for a transmission issue (ie shuttering, stalling). other thought is it may be a fuel pressure issue or fuel quality issue. You can test for fuel pressure using a meter on the valve on the end of the fuel rail. Check out volvotips.com for the spec - I think its in the 40-45 PSI range. You want to rule out a weak fuel pump (usually relays go because of a bad pump) or a fuel filter issue (the round cannister with the fuel lines in front of the rear wheel)

 

Thank you. I will look into the plug wires