Hi,
I have a 1982 volvo 240 that backfires in spite of recent major tune up, new radiator, water pump, timing belt too. It is running a bit rich, which helps the backfiring. I am told the air flow meter is “worn out”, and replacing it will cure backfiring issues.
I am dubious after being told the tune up was the cure – and it wasn’t. The car backfires when cold or moving from a stop. It has 205K, and is a manual with overdrive button.
Any insights appreciated. I also have a v70 with issues, more on that later!
If it is running rich, when was the last time you replaced the O2 sensor? This car is 26 years old, and O2 sensors should be replaced every 60K or 5 years. Also, a Hanyes manual has testing tips for most of the sensors on this car. You need a multimeter to do most of the testing, but the instructions are there. I would definitely test before buying replacements. Throwing parts at a problem is an expensive way to fix it.
It probably has centrifugal, and vacuum, advance. Lubricate the moving parts inside the distributor: http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c15280063e77
Loosen, and turn, the distributor 1/4 inch clockwise, and see how it runs. If the misfire is worse, loosen and turn the distributor 1/4 inch the other way.
Make sure it has a clean fuel filter, and that the fuel pressure is ok.