We just bought a 2004 Volvo c70 was doing good for a couple of weeks. Started with stalling out when trying to accelerate. Now it starts and runs but has a very rough idle and when trying to take off I can only get to 30min and then the rpm starts to climb. It sounds like it is taking in too much air somewhere not sure where though. We did put it on the computer and it had a mass air flow sensor code so we reset it and replaced that part, has new battery, alternator, air filter, fuel filter and spark plugs. The engine light is on and flashes but I do not have access to the computer right now. Any thoughts?

 

Start by buying or renting (ie from Autozone) and OBD2 code reader. It will plug into a port under the drivers side dash (kind of looks like an old school printer port). That will tell you what fault codes are causing the check engine light and give you a chance to clear the codes. If they come back, redo the scan and research how to diagnose from there. Note on your car, you have an electronic throttle mechanism (ETM) which are prone to fail. Check out the Xemodex web site for common symptoms and a diagnostics flow chart to see if you're needs to be rebuilt. Also another thing you can do at home is to look for obvious intake air leaks - inspect vacuum hoses and intake air boots for tears/cracks/poor fitment, spray around these areas with flammable carb cleaner (if any gets sucked in you'll see it and it will bump the idle). Sometimes it requires a shop to do a smoke test for hard to reach air leaks. Other possible causes could be fuel pressure - a wonky pump or pressure regulator. Reason I note all this is quite often the MAF and things like O2 sensors get blamed for fuel trim issues when there's other possible causes that need to be sorted out. It would be useful to post up the original fault code that led you to replace the MAF. Last comment - some Volvos are very sensitive to the MAF brand. Not all aftermarket products (even "compatible" Bosch parts) agree with these cars. When in doubt, try swapping the old MAF back in to see if anything changes for good or bad.