Hi 1973camaro, Welcome to 2carpros and TY for the donation
Engine running rough or misfiring can be cause by the following: 1. Defective spark plug.
2. Inadequate spark/coil, defective spark plug wire.
3. Lack of compression
4. False air leakage.
5. Faulty fuel injectors.
6. Insufficient fuel pressure.
7. Contaminated fuel.
8. EGR valve that is leaking.
9. Oxygen sensors.
May, 16, 2010 AT 9:48 PM
Call Volvo to see if you are still withing the 10year/200k mile extended warranty for the electronic throttle. If diagnosis reveals the throttle is faulty and you are still withing the extended warranty period, Volvo will replace it at no charge to you. Also the PCV system will need to be cleaned out if plugged. If the breather box is plugged up, you will be responsible for the repair and you will be responsible for paying diagnosis if fault tracing reveals that the throttle is ok. Keep me posted.