I have a 2004 Volvo XC90. It has just over 120k miles on it and I just bought it used a few months back. All of a sudden one day my check engine light turned on but everything seemed to continue to run normally. A few days later I was at the store and I came out to return home and started my vehicle and I could tell something was wrong....my car started fine, but once it started my RPM's sit and jump around between 1-2 and while it does that my car makes a chugging kind of noise and my interior lights seem to flash dimmer and brighter. If I try to drive with it like that it reverses perfectly, but if I try to accelerate forward I can't go more than 10-15 miles per hour, even with the pedal to the floor. It does this almost every time I try to start my vehicle, once in a great while it will start regularly and everything works as though nothing was ever wrong....I have very little knowledge of cars (almost none) and I was just wondering if anyone knew what it might be? I need to take it in to a mechanic to look at, but I can't call to schedule anything because I don't know when it will start regularly for me to drive it there. I'm a single mom with very little support, I was hoping someone might know what is going on and could help me figure out if it is going to be a big expense to fix (fingers crossed it is not). Please let me know! Thanks in advance!

 

Step 1 is to get the mechanic (or friendly auto parts store) to read the OBD2 fault codes that set off the check engine light. Those codes are typically a letter followed by four digits (ie P1004 ). The likely cause of your symptoms are either fuel delivery (fuel pump relay, fuel pressure sensor, fuel pump) or a fuel mixture sensor - Mass Airflow sensor (MAF), air pressure sensor (ie the MAP) or the electronic throttle body (ETM). The ETM and MAF can become dirty and may benefit from a cleaning but a mechanic will likely opt to replace the parts. The ETMs are very expensive to buy replacements when they fail but there are services that will rebuild if that's the cause. See if you can jot down the OBD2 codes and post up and that will give a clue as to what to expect.