Hello friends. My 1985 Volvo 240 (B230f) was running just fine until I was heading to a gas station to top up. She started to sputter and caugh, then just petered out. I assumed it was because I was very low on fuel if not completely out. So when I put a couple extra gallons in I thought she would start right up but it didn’t turn out In my favor. I tried a few things but to no avail. So when I got to a garage they fixed it up saying the spark plugs weren’t tuned right and the mass air flow sensor was gunned up. So I drove her about 40 miles and the same thing happened again. Now I’m stuck and I don’t want to fork another $400 for nothing. To me this problem revolves around the mass air flow sensor, should I just replace it or is there a way of getting it jumped again like the garage did?

 

Hi DW, gave you a free lift over to the 240 board where there's a good crew of experts. Sounds like your mechanic needs to sort out a few things. The mass airflow sensor is doing the metering for the fuel injection system - it doesn't directly relate to spark plugs, but if its off and your car starts to run rich, the plugs will turn black from the excess fuel. The mass airflow sensor is really a grid of wires that change resistance based on the amount of air flowing by the wires. If the wires are dirty the metering will be off. You can try cleaning with a special product like CRC MAF cleaner but sometimes the part will just need to be replaced. With that said there are other things in play in fuel metering - if you have a cracked air boot, broken vacuum lines, bad O2 sensor (aka the Lambda sensor) or a dirty or failed idle air control valve, the fuel mix may be off. Modern fuel injection systems also use temp sensors, altimeters (aka the MAP sensor) to tune the fuel mix. There is also the fuel delivery side of the equation. is the fuel pressure correct or are you getting too much or too little fuel? So long way to get to your question about should you replace the MAF sensor? It comes down to what other symptoms and tests have been done to identify that as the failed part? $300 is a lot for a replacement part, so the tech should be doing some tests to determine the correct root cause. If you are planning to do the work yourself, you can try cleaning or try unplugging the MAF to see if the car will start up w/o it then go from there.

 

Sounds like the MAFS. Cleaning it rarely if ever works. if the plugs are contaminated with fuel, they will need to be changed too... No OBDiagnostics on your car so only swapping the MAFS will tell if you are on the right track--that's the "fun" of fixing these cars.