1999 Volvo S70 Hard Starts

Why did you replace the oxygen sensor and mass air meter to begin with? Also do you have any trouble codes stored in the engine control module?

Sorry but I could not find that code? Do you have any codes now? Also when you checked the fuel pressure, pressure should be between 375-395kpa with engine running. When you shut it off, residual pressure within 20 minutes after fuel pump shut off should be 200 kpa.

If that is O.K. Then call Volvo and give them your VIN# and see if campaign 155 has being done? If not take it in to Volvo for it. That is free of charge to you. If it has being done already, find out if the extended warranty for the throttle has expired or not, If still under warranty you will need to take to Volvo to have them diagnsose the throttle to see if it is bad or not. If it is still under the 10 year/200k mile warranty they will replace the throttle if it is bad. If not you will need to pay for for diagnosing and repairing. If you are out of the extended warranty, try cleaning the throttle. I recommend buying the cleaner from Volvo since most carb cleaners will destroy the throttle since it is a control unit itself. Hope this information helps you.

Your problem almost seems familiar with a car I had problems once also? Hard to start at times and check engine light? Try this. When you start the car up try to wiggle the engine control module. The module is located on passenger side towards the fender. Remove the cover yu will see 2 modules. The once closest to the fender is the ECM. The other one is the transmission control module. You can not remove the module unless you have the special tool to remove it. Kinda twist around gently. If the car dies then your module is bad.