I've recently bought a Volvo V70 I 2.4 (106 kW, gasoline, 1998), and on the way back home from the seller the car died several times when starting from a standstill, until finally a few hundred meters before my home it wouldn't start anymore. Had to have it towed (ouch), where I then started to investigate the issue.
What I've done so far:
Many people on the internet who had similar issues replaced the fuel-pump control relay to fix the issue. In fact bridging the relay let my car start again (that piece of wire went straight into the glovebox). I've ordered a replacement part and my car would start normally again and seemed to work fine at first. I've also checked the fuel pump if it still worked by disconnecting the fuel line after the filter, and a squirt of gasoline came out when turning the key.
I hoped the only issue would be the faulty relay, but apparently this is more complex. When I accelerate too strongly, the engine will rev down immediately and die, and most of the times will not recover. When accelerating lightly, it revs up just fine. At speed the engine keeps going, but sometimes is a little bumpy.
- Fuel Pump: I have already bought a replacement pump. Maybe the current pump has deteriorated and killed the fuel pump relay? I'm replacing this to be on the safe side because the part is cheap enough.
- Mass Flow Sensor: Mabye this is the culprit? Sadly I have no oscilloscope to check this whatsoever. Will try cleaning it with special cleaning spray.
- Lambda Sensor: Could a faulty lambda sensor cause the issues? Wouldn't that light up the indicator on the dash?
- Throttle Valve: This is a mechanical valve with a pulley system, could it be dirty and thus lag and cause issues? Does this have a sensor of sorts that could be faulty and thus cause not enough fuel to be injected?
- Ignition system: The car has a ignition distributer. Could faulty spark plugs and/or worn distributor cause the issue?
Could any of these be the cause of the issue? What else could cause this issue?